A sleek black aircraft descends through the clouds to planet Mobius. Doctor Robotnik, the planet's absolute ruler, is returning home to Robotropolis, a sprawling cityscape choked with the smoke of innumerable factories. Robotnik strokes his robotic bird, Cluck, saying "I do miss the beauty of this place when I'm away". The aircraft settles on a landing platform on one of the tallest buildings, where Robotnik's toady Snively waits to greet him. As Robotnik enters the control room, Swat-bots open the door to let him in, but when Snively tries to enter the Swat-bots close the door, and Snively bumps into the closed door, and the two Swat-bots chuckle, since he fell for their prank. In the control room, Robotnik demands to know if there has been any hint of his nemesis, Sonic the Hedgehog. Snively is too cowardly to admit that there has been none, and stammers for a while until an emergency appears on monitor 10. Scanners have detected one of Sonic's group of Freedom Fighters: Snively recognizes him as the young Tails, usually accompanied by Sonic. Robotnik says to capture him. "Perhaps his cries will flush out the hedgehog!".
Meanwhile, Tails is out picking flowers for Princess Sally Acorn when he spots one of Robotnik's Buzz-Bombers bearing down on him and he flies away. Not far away, Sonic the Hedgehog demonstrates a new rock song for his pal Rotor Walrus. Sonic wants to impress Sally, but Rotor says she won't like it. She'd prefer a softer song, like a ballad, but Sonic can't stand ballads. Suddenly, they hear Tails crying for help. Sonic speeds to the rescue, whisking Tails out of the way of the Bomber's sting blast, which ricochets off a rock and destroys the Buzz-Bomber! Rotor draws their attention to a floating eye camera. Sonic and Rotor use the opportunity to insult Robotnik, who is watching from a monitor, but Tails simply waves and says "Hi mom!" Before they go, Robotnik swears that he'll have both Sonic and the Power Rings in the palm of his hand before the day is through. The three Freedom Fighters are not impressed, and Sonic zooms away with his friends in tow.
Soon after, the three heroes arrive at the secret entrance to their home at Knothole. Tails enjoyed riding with Sonic, but Rotor feels decidedly queasy. Sonic and Tails ride together down a twisting slide that takes them into Knothole and drops them in a haystack. Moments later, Rotor follows, landing on top of them.
Some time later, the Freedom Fighters (Sally, Bunnie, Antoine, and Rotor) attempt to repair some catapults. Bunnie, a cyborg, does the heavy lifting and is annoyed by Antoine's habit of "supervising" while doing no work of his own. Antoine also flirts with Princess Sally, who rebuffs his advances. Sally uses a computer to determine why the throwing arms of the catapults keep breaking, and finds the answer just as Rotor deduces it all by himself: the cotter pins are made of wood, but need to be metal in order to take the extra payload. Just then, Sonic arrives. When Sally explains that they need metal cotter pins, Sonic takes Rotor and says they've "gotta do the Power Ring thing!" He, Rotor and Tails go to the Lake of Rings, and as they watch a Power Ring rise out of the water. Tails wonders why only Sonic can use the Power Rings, so he explains: his Uncle Chuck invented them to help Sonic take down "dorks" like Robotnik.
While Sonic waits to get an example cotter pin from Rotor, Tails decides that he's going to head to the "big city". When Sonic catches him up, he is fighting a tree. Sonic explains that the big city is too dangerous for a kid like Tails: it's swarming with Swat-bots, who are just waiting for a chance to roboticize Tails! Tails points out that it's a long way back to Knothole and he could be captured by a Buzz-Bomber, so Sonic agrees to let him tag along as long as Tails stays hidden in his backpack and guards the Power Ring.
In Robotropolis, Sonic and Tails narrowly avoid detection by Swat-bots. They reach one of Robotnik's factories, where they manage to find the cotter pins in a pile of debris. However, Tails spots a line of worker robots walking into the factory. Sonic explains they used to be people, until Robotnik roboticized them. Tails asks if Uncle Chuck is there, but Sonic doesn't see him. Sonic misses Chuck, as well as his old dog Muttski. Suddenly, Tails sees a mean-looking robot guard dog: it's Muttski! He may look vicious, but Sonic believes Muttski won't hurt him because Sonic is his best bud. He calls out to his dog, only to have Muttski pounce and bite his tail. Sonic is disappointed, since after all he put Muttski through four years of obedience school. "Bad dog! You sit, you stay, you don't bite! Understand?" Suddenly, Muttski does just that - his eyes turn from red to white and he sits, and starts wagging his tail. He's Sonic's friend again! He licks Sonic's face and Sonic promises to turn him back to a real dog by putting him back through Robotnik's robo-machine. Unfortunately, Muttski's old personality doesn't stay long, and he quickly turns back to a savage, red-eyed guard dog. Sonic flees rather than fight his friend.
While escaping from some Swat-bots in the city, Sonic and Tails dive into an air vent. It turns out this vent leads to Robotnik's control room, where Robotnik is explaining his latest plan to locate Knothole Village and eradicate the Freedom Fighters. His Buzz-Bombers will fly over the Great Forest, spraying it with a new chemical that Robotnik invented, which will kill every tree, exposing Knothole's location. He also has a "hedgehog-seeking missile" prepared, in case Sonic should interfere. Just then, Tails sneezes with such force that he and Sonic both fall into the control room. They quickly escape the building, however, and Sonic uses the Power Ring to increase his super-speed even further and defeat the Swat-bots sent to capture him. He and Tails speed back to Knothole.
Sonic quickly warns everyone about Robotnik's plan, but luckily Sally has a plan of her own. When the Buzz-Bombers approach, the Freedom Fighters set up the now fully-functional catapults in a line at the edge of the Great Forest. However, Sally says that the range is limited, and Sonic volunteers to lure the Buzz-Bombers in range. Using one of the catapults, Sonic shoots himself towards the incoming Buzz-Bombers, leading them to launch the hedgehog-seeking missile. However, Sonic is able to turn this against them by leaping on top of the tanks of Robotnik's defoliating chemical. The missile hits the tanks, which fall to the ground far below. Robotnik orders the Buzz-Bombers to attack Sonic, who leads them in range of the catapults. Sally gives the order to fire, and they pelt the Buzz-Bombers with water balloons, short-circuiting them. Robotnik demands through the radio that they keep attacking, but the Buzz-Bombers have had enough, and flee. Robotnik decides to take his frustrations out on Snively.
Safe once again, the Freedom Fighters celebrate, and Sally says that Sonic was "really great today!"
In Robotropolis, a green security SWAT-bot is carried by floating platform to one of the industrial building's elevators. The elevator takes the transport downward in the elevator, the floor indicator counting upwards until it shows "51." The doors open and the transport enters a large room, where it faces a yellow security bot that transmits the message "Hall secure." In an air duct, undetected by the robots, Sonic the Hedgehog speeds through until he stopped at a vent, calling for Antoine and Cat to hurry up as they pant down the duct after their friend. When they arrive,
Sonic checks the room, only to come face to face with the green security bot. The three Freedom Fighters jump back against the wall as the transport removes the vent and points a light into the duct. The security bot's windshield opens to reveal that Princess Sally was commanding it. Greeting her fellow Freedom Fighters, she jumps from the transport and, accompanied by Sonic, enters a robotic plane. Using Nicole, Sally aims to hack into Robotnik's mainframe computer in order to reprogram the plane's launch data. While working, however, she receives a message addressed to "Bean". Sally's father used to call her Bean when she was little, and she immediately starts tracking down the source of the signal, believing that he may still be alive! The signal apparently originates from the Dark Swamp.
Back in the air vent, a nervous Antoine leans against the grill, toppling out of the duct and straight in front of a security Swat-bot! Ant dives back into the duct. Realizing that their cover is blown, Sonic goes to distract the Swat-bots while Sally makes a dash for the duct. When she is safe, Sonic makes his own escape. However, a single Swat-bot follows Sally, Ant and Cat into a duct. Cat, who is bringing up the rear, spots it and decides to lead it away from the others. Only when Sonic meets up with Sally and Antoine at their preset rendezvous point do they realize that Cat is gone. Sonic realizes he must have been captured, and wants to go back to save him. Sally, convinced that the signal was from however, says that she is going to go to the Dark Swamp to find him, and she'll take Antoine with her. Sonic says he'll catch up once he's rescued Cat, and speeds back to Robotropolis.
Meanwhile, Snively reports back to Doctor Robotnik, who orders the air ducts sealed up. Snively does have some good news. They have captured a Freedom Fighter: Cat! Robotnik wants Cat to tell him the location of Knothole, but Cat refuses to talk.
Some time later, when Sonic arrives back in Robotropolis, he sees Cat being taken by a Swat-bot to a detention center. Although Sonic breaks in and reaches Cat's cell, Cat tells him that Robotnik's surveillance detected Sally heading for the Dark Swamp, and that Sonic has to go save her. Sonic doesn't want to leave Cat, but Cat says it doesn't matter. As guards show up, Sonic escapes, promising he'll be back.
A Surveillance Orb follows Sally and Antoine through the Dark Swamp. Antoine is terrified, but tries to dismiss his trembling as shivering from a cold he as caught. He wants to go back to Knothole, but Sally isn't willing to give up. She asks Nicole about whether there are any structures in the Dark Swamp, and Nicole identifies only one: Ironlock Prison. When Sonic arrives at the swamp, he is also detected by a camera, leading Robotnik to launch a Stealthbot. However, it is easily defeated by Sonic, who turns its own missile against it.
Sally and Antoine arrive at Ironlock Prison and try to cross the rickety drawbridge over a deep chasm. Although they make it to the other side, the bridge collapses, leaving them stranded. They explore the prison, finding a scrap of King Acorn's cloak—Sally now has proof he was there!
Sonic, Sally, and Antoine search Ironlock for information regarding the King. At this point, Sonic catches up to them, having been following their footprints in the swamp mud. He leaps over the chasm and finds Sally and Antoine walking through the prison cells. Sally shows him what they've found: an ancient computer. Sally realises that her father must have sent her the message from this computer. When she accesses it, using "Bean" as the access code, she receives a message: "Bean, Check Sub-ter file. Impossi—" The message is incomplete, but at least Sally now knows he is alive. When she checks the computer's Sub-Ter file, she finds it contains schematics of the underground tunnel network throughout the whole of Robotropolis! As she tries to get Nicole to transfer the data to a holographic disk, the walls start to crumble and all three heroes are sent through a trapdoor into the sewer system below. They then see a red light in the distance, within the darkness of the only passage out of the sewers, and Sonic decides to go and check it out. But when he comes back, he states that they cannot go that way, as the red light turns out to be the glow of the eye of a giant one-eyed monster, which then attacks Sonic and his friends. But Sonic manages to defeat it by using a Power Ring, revealing that it is merely a robot.
With one obstacle out of the way, Antoine brings up another: how are they supposed to get out of this place? Bringing up the holographic map on Nicole, Sally gets a great idea. She leads the others down one particular tunnel, straight into Robotropolis. Using the secret tunnels, they access the Stealthbot hangar bay, and Sally reprograms every single one. While Sally and Antoine head back to the usual rendezvous point, Sonic has one last job to do: rescue Cat. But when he gets to Cat's prison cell, Cat has gone! Saddened by the loss of his friend, Sonic makes his escape. He is detected by Robotnik's surveillance, leading the dictator to launch all of his Stealthbots.
Back at the rendezvous point, Sonic and the others see the Stealthbots launching. Taking out a Surveillance Orb from his backpack, Sonic points it at the Stealthbots. When Robotnik sees the feed, he is confused and orders the Stealthbots to be recalled. However, as Snively presses the recall button, the Stealthbots all self-destruct! Turning the camera on himself, Sonic gives Robotnik one last message: "That was for Cat!"
After trying to detonate one of Robotnik's machines, Sally gets captured by Dr. Robotnik's Swat-bots. Sonic tries to go back, but Bunnie tells him he needs a power ring if he's going to save Sally. Meanwhile, Robotnik creates a clone of Sally to use to try to destroy Knothole. Sonic gets the power ring the next day and rescues Sally, but doesn't realize that it was the clone that Robotnik created. Sonic and the cloned Sally returned to Knothole. Tails found out he didn't get the "Funny Kiss" (on the nose) that Sally usually gives him. Then the clone reads a book to Tails and asks her to do the scary witch voice but refused and walked off. Sonic then, finds out that the SWAT-bot factory was still online and decides to go back and redo the mission. While in bed, Tails sees the cloned Sally and he sees the eyes glow red and finds out that it wasn't the real Sally. Bunnie wakes Sally up and showed her the ruined carrot crops, and Tails thinks it was the "Fake" Sally who did this during the night. Before going to the factory, Tails tries to tell Sonic that it wasn't the real Sally, Sonic thought Tails had a nightmare and ran off.
While at the SWAT-bot factory, Sonic does the special handshake that he and Sally do, and finds out that Tails was telling the truth, that it wasn't Sally. After subduing her, the clone shows Sonic the way to the Real Sally, who saves her before she was robotocized and run back to Knothole while putting the clone in Sally's place inside the roboticizer, overloading it and destroying the factory. Back in Knothole, Sally finds Tails sitting by the log and gives him the "funny kiss", proving to Tails that she's the real Sally (Adding more proof with the "scary witch voice"). She attempts to prove it by giving Sonic a kiss, but this makes Sonic claim that she's fake so he grabs Tails and runs off.
While spliting up into teams, Sonic, Sally, Antoine, Bunnie, and Rotor are forced to flee Robotropolis in mid-plot. Their rendezvous is a train station, where Sonic's roboticized Uncle Chuck boards a departing train. The Freedom Fighters follow the train to the crystal mine to try to rescue him. Unsurprisingly, he is not the hedgehog he used to be, but Sonic temporarily fixes that with a power ring. Returning to Knothole with the freed Uncle Chuck will have to wait, however. The robots are excavating a powerful crystal, which will further Dr. Robotnik's goals and wreak havoc across Mobius. This leads to Chuck going back to robotic form, while telling Sonic to leave Robotropolis while he still can. But Sonic protests so Bunnie brings him on the train herself against his will of not wanting to leave his uncle again. Back at Knothole Sonic is comfort by Sally and Bunnie telling him that they will get Chuck back, to which sonic agrees to.
The Freedom Fighters embark on an outlandish mission: to find magical scrolls which may hold the key to unlimited power.
As Rotor was working on a waterwheel to spread electricity through out Knothole Village. While Sally was searching for information on the waterwheel in Nicole's databanks, Nicole began malfunctioning. To fix the malfunction, Sally needed a computer chip. The only place she could get the chip was in Robotropolis. So she and Sonic went to go get the chip.
When they got to Robotropolis, Sally went into the room where the chips were, while Sonic waited outside. She picked up a chip and turned around only to be face-to-face with a SWAT Bot. She turned and ran as the robot chased after her. As she ran, she noticed a place called the Forbidden Zone. She ran in but stopped when she saw a cloaked figure with glowing red eyes standing in front of her. The cloaked figure shot an eye-beam, but instead of shooting at Sally, it shot and destroyed the SWAT Bot. Sally ran out of the Forbidden Zone before the figure turned around and decided to shoot her, too.
She met up with Sonic and they left for Knothole. While at Knothole, she installed the chip into Nicole and researched what the hooded figure was. Nicole said that it was called "The Guardian". The Guardian protected its master, Lazaar, from anything that entered the Forbidden Zone. Lazaar was a wizard who lived in the Forbidden Zone. He had been asleep for a very long time and he was also thought to be very evil. He had a magic computer that, like anything magic, can cast spells. Sonic had the idea that if they got the computer, they could use it to stop Robotnik. Meanwhile in Robotropolis, Robotnik had seen the whole thing and was also curious as to what the hooded figure was. He, or actually Snively doing it for Robotnik, was reasearching the same thing.
So, Robotnik decided to have a talk with the Guardian. Robotnik convinced the Guardian that he was also evil and wanted to talk to Lazaar and congratulate him on his evilness. Robotnik found out that the only way to survive the traps surrounding Lazaar's lair is to be pure evil. The Guardian showed him a map and told Robotnik to come alone.
Later, Robotnik's hover craft lands in the Forbidden Zone. First he sends out a SWATbot to survey the area. As it looks at the Forbidden Zone, it sees it has many pools of purple stuff that, when an uninvited guest walks by, a hand shoots out and grabs the intruder. Also, on the far side of the zone, the entrance to Lazaar's keep can be seen. It looks like a giant mouth which crushes intruders to a mushy pulp. As the SWATbot enters the Forbidden Zone, it is grabbed by a hand in the pool, but escapes. Just before the SWATbot thinks it can enter the doorway to Lazaar's palace, it closes and crushes the robot. Robotnik merely smiles and walks in. When he passed a pool, it retained it's quietness and serenity. As he nears the door, it opens and allows him to step in. He walked through the halls of the lair until he came upon Lazaar's resting place. But, Robotnik didn't want to talk to him, he wanted the computer. When he took it, it set off an alarm and Lazaar began to slowly return to conciousness.
Meanwhile, Sonic was running through Lazaar's lair, also trying to find Lazaar. When he got to Lazaar's resting place, the computer was gone and Lazaar was awake. Lazaar appeared in front of him and blamed him for stealing his computer. Sonic tried to explain that he didn't do it, but Lazaar didn't believe him and trapped him in a bubble. Lazaar told Sonic that someone was using the computer for evil. He then said that he was once evil, but, because he was asleep for so long, he began to dream about what his evil had done to people. Sonic immediantly knew who it was: Robotnik. He said that he can get the computer back, if Lazaar would let him go. So, Sonic agreed and revved up to leave. But before he could leave, Lazaar took away his speed. Sonic protested, but he could do nothing about it.
Back at Robotnik's lair, he has activated the magic computer and was looking for spells. He decided to teleport Sally and Bunnie to his base. He put them under mind control.
Sonic began making his way through the polluted city of Robotropolis even without his speed. A hover craft zoomed by. Another zoomed by, but this time, Sonic jumped on to it and hitched a ride to Robotnik. When the craft landed, he jumped off and began wandering the halls of Robotnik's lair. Suddenly, a laser flew by. He turned around and saw SWAT Bots chasing him. They chased him trough the halls and down a stairwell. Sonic left a bomb on the stairs. The bomb detonated just as the SWAT Bots passed over it. He continued running down the stairs, but he was suddenly engulfed in light.
When the light dispersed, he was in between Sally and Bunnie (who, if you remember, were under Robotnik's mind control). Robotnik gave the order and they lunged at Sonic in an attempt to grab them. They held Sonic's arms to keep him still. Robotnik began tell the hedgehog that there was no escape, but of course, Sonic always escapes. Robotnik then gave the order to have Sonic roboticized. Sally and Bunnie dragged him over to the roboticizer. The glass was about to shut, but Sonic caught a glimpse at Lazaar's computer. He shook free of Sally's and Bunnie's grip and jumped to the magic computer. He picked up and ran. Sally and Bunnie chased after him. A SWAT Bot noted that Sonic had the computer. It was going to shoot the hedgehog, but Robotnik began shaking its arm and telling it to hurry. This caused the SWAT Bot to lose aim and fire at a net of barrels on the ceiling.
The barrels fell and blocked Sally and Bunnie from reaching Sonic. Sonic ducked beneath a computer console to escape from being crushed. He had nowhere to go but back. On the other side of the barrel mess, Bunnie was moving the barrels out of the way. When they removed the final barrel, Sonic plowed through them, giving them his pardons of course. He began running to another exit. Before he could make it, Cluck flew to him and knocked the magic computer out of his hands. Before Robotnik could grab the computer, Sonic jumped up and grabbed it. He then pressed a button on the computer and cancelled the mind control spell cast on Sally and Bunnie. They woke up in a confusion and asked Sonic what he was doing here. He said he'd tell them later and they began running. They ran down a tunnel and Robotnik followed along with a robot. The SWAT Bot kept running. Robotnik stopped and claimed how he hated Sonic.
When Sonic got back to Lazaar's quarters, he returned the computer to the old wizard and offered him to join the Freedom Fighters side. He refused because he needed to keep his magic computer out of the hands of evil ones. He then pressed a button on his belt and returned Sonic's speed. They said their goodbyes and their good lucks. Lazaar walked back into his palace. It began to glow and disappear. Sonic, Sally, and Bunnie began walking back to Knothole, but was teleported there as a gift from Lazaar.
They arrived at Rotor's workshop back in Knothole just in time to see Rotor activate the waterwheel and the light.
When Sonic, Sally and Bunnie are attempting to destroy the main generator in Robotropolis. While they manage to do just that, they completely forget about the backup generator, so their victory is bittersweet. Back at Knothole Village, the Freedom Fighters hear about a race that Robotnik is holding; Sally knows it's a trap, but Sonic decides to enter the race anyway, in hopes of distracting Robotnik while Antoine, Bunnie and Sally are heading off to destroy the backup generator.
Jealous of all the popularity that Sonic gets from the other villagers (especially Sally), Antoine tries to capture Robotnik on his own, using a Power Ring as bait. Unfortunately, his plan backfires and Robotnik uses the Ring to power his Sonic Radar.
When Robotnink launches a Spy-Orb that will uncover the Freedom Fighters' Knothole location, Rotor launches them up to the orbiting spy-sphere aboard a home-made rocket powered by Robotnink's discarded booster engine that fell in the Great Forest. Once aboard the heavily guraded sphere, Sonic and Rotor must find the spy sensors before they locate Knothole.
Sonic is paralyzed by a recurring nightmare personifying his own personal fears; meanwhile, Robotnik unleashes a machine that can literally destroy the world.
The Freedom Fighters find themselves defending an underground city of Mobian refugees, all the while coming to terms with their own personal relationships.
The Freedom Fighters home, the Great Forest, is dying. In search of magical water that causes plants to grow at an accelerated speed, the Freedom Fighters journey underground where they begin disappearing one by one.
Robotnik and Snively discover an underground oil lake and start drilling, but their robotic snake probes disturb a purple subterranean creature. They also inadvertently block off a green underground stream, forcing the mysterious green water to rise to the surface and flow into the Great River.
Meanwhile, Sally, Rotor Walrus and Tails attempt to grow some trees in the area around Knothole, but find that nothing will grow. In fact, even the trees in the Great Forest are dying—Robotnik's pollution is spreading faster than they thought. Elsewhere, Sonic the Hedgehog is fishing at the Great River. A huge fish snags his fishing pole, pulling it and Sonic himself into the water. Sonic water skis behind it for ten miles (apparently) before being shaken off. When Sonic tries to explain the story to the other Freedom Fighters, he shakes water from his ear onto the withered tree shoots, which suddenly grow very large. Sally decides they must try to get more water from the Great River, and takes Sonic, Rotor and Antoine on a boat to get some. Sonic is impressed by Rotor's boat, although Rotor says he'd rather be a hero than a handyman. Suddenly, the boat is sucked down a whirlpool and spat out in an underground cavern, which seems to have been used as a dumping ground for Robotnik's garbage. As they try to navigate the tunnels, Antoine disappears.
Sonic, Sally, and Rotor row their boat into strange rainbow-colored water, which suddenly begins to boil and turn pink. They abandon ship just before it sinks, and discover a cavern filled with beautiful plants—some of which have teeth and try to attack. As Sonic ties up the man-eating flowers, Sally disappears just like Antoine. Sonic and Rotor find what seems to be a palace or throne room, but it is filled with more of Robotnik's trash and there is nobody home. They hear a noise, and Sonic goes to investigate only to be captured by the purple creature from earlier in the episode. Rotor manages to escape by accidentally tripping into a hole. Rotor discovers an even deeper chamber, also filled with plant life, where a green river has been blocked off by fallen rubble. He unblocks the river—the audience is shown that roots from the Great Forest are fed from the river, and so had been dying while it was blocked off—then collects a sample of the green water in his canteen.
Rotor finds Sonic, Sally, and Antoine, who have been stuck up to their necks in a lake of Robotnik's pollution. He helps Sonic reach a Power Ring, and together they rescue Antoine and Sally. Rotor is hailed as a hero. The four Freedom Fighters again encounter the purple creature, who accuses them of polluting his world and thereby killing all the other members of his species. They explain that Robotnik is really responsible, and that he has polluted their world too. They are attacked by Robotnik's snake probes, and on Rotor's advice Sonic runs up to the surface to deactivate Robotnik's oil platform, which he does.
Underground once more, Rotor uses the green water sample to turn the oil lake into clean water. Although there is not enough water to save the Great Forest, their new purple friend gives them something that could help, and Sonic offers to take him fishing any time. On the surface, Sally uses the remaining green water on their tree shoots, which begin to thrive. Rotor admits that being a hero is exhausting, and that from now on he'll stick to being a handyman.
Robotnik has set his greedy eyes on the last living herd of a dinosaur-like species. The Freedom Fighters help the creatures navigate through the Great Jungle while fighting off the advances of Robotnik's machines.
While salvaging a wrecked hover pod, the Knothole Freedom Fighters see a pair of Swatbots chasing a ram named Ari. Princess Sally incapacitates them with an electromagnet. Ari explains that he's the last member of a group of freedom fighters that was captured by Robotnik. Sally is suspicious, but Sonic agrees to help Ari save his friends.
At Knothole, the others tap the memory banks of one of the Swatbots chasing Ari and realize he's leading Sonic into a trap. Ari and Sonic travel to a mechanized pyramid where Ari traps Sonic inside a giant pinball game, with Sonic inside the ball. The more points Robotnik scores, the more a portal to the Void opens.
Sally and Dulcy fly to the pyramid to try to warn Sonic but are stuck outside and instead fly after Ari when he leaves in a hover pod. He flies to meet Robotnik, who promised to release Ari's friends if he helped capture Sonic, but shows Ari that his fellow freedom fighters have already been roboticized. They save Ari from a similar fate and return to the pyramid. Ari saves Sonic but is sucked into The Void after telling Sonic to look for the king's list of other freedom fighter groups.
While on a mission, Sonic and Sally spot Robotnik's Shriek-bot and also spot Sonic's Uncle Chuck working on the Shriek-bot. Trying to get to his uncle, Sonic sneaks toward him but Snively and Robotnik spot him. Robotnik orders Snively to activate the Shriek-bot and when Sonic was close, he gave chase. Sonic then tried to outrun the flying bot (which carrying Sally) but the mech nearly caught up to him but Sonic managed to pull out a Power Ring and escape.
Angered, Robotnik yells Snively's name, to which the latter squealed in fear. Robotnik claimed that Snively "lied" about being able to outrun Sonic. When Snively tried to reason with him, he asked him "what color is my heart?", to which Snively claimed that he could not see one.
In Knothole Village, Tails tries to sneak past a (seemingly) sleeping Dulcy, but the dragon stops him, telling him that Sonic and the others are working on something and didn't want to be disturbed. Inside, Sally activates the De-Roboticizer to change Bunnie back to her normal, organic self. This was a success and Sonic runs off to the Lake of Rings to get a Power Ring before he goes to Robotropolis to free his uncle. Sally warns him that they don't know how long the effects will last, but Sonic doesn't listen and speeds off. Once at Robotropolis, Sonic slips his backpack with the Power Ring in with Chuck's tools. Picking it up, Chuck regains is free will and follows Sonic back to Knothole so he can be de-Roboticized. Sally tries to De-roboticize him, but as Nicole states, there is a malfunction and Chuck is still a Robian, and to make matters worse, Robotnik's programming kicks in and the Freedom Fighters are forced to put him in a cage.
After finding Uncle Chuck's message, Sonic goes to find a chili dog vendor in Robotropolis. After he gets it, he finds more Freedom Fighters who are about to be roboticized. When he saves them, a Trackbot hits him with a laser that erases his memory. Snively, who is commanding Robotropolis because Robotnik has gone out for the night, then tells him that he is his friend and tells him to find Knothole. Sally warns the other freedom fighters that Sonic is going to tell Snively where Knothole is. Sally, Tails and Charles find a Power Ring and decide to use it to restore Sonic's memory. Before Sonic sets off to stop Snively Sally then tells Sonic that she is so glad that he was back and gives him a kiss. When Snively arrives, he starts erasing the other Freedom Fighters' memories one by one, only for Sonic, who has had the Power Ring in his hand to restore his memory, to erase his. Sonic tells him that Robotnik is a "bottom-dwelling scum-sucker" and Sally moves Knothole's coordinates to the Great Swamp. Robotnik returns, defeats Snively and threatens to turn him into a paperweight. However, Snively tells Robotnik he's found Knothole, somewhere in the Great Swamp. Therefore Snively and Robotnik searching for Knothole in the Great Swamp.
The episode starts with an eerie picture of Robotropolis, followed by the the entrance of Sonic, Sally, and two other Freedom Fighters. Sonic and Sally have a quick chat about the plan, and Sonic rushes over to two Robots and gives them the usual sarcastic remark. He then drives them away from the Freedom fighters. They then proceed in, according to Sally's plan, and a power surge follows. Soon after, through binoculars Sonic and Sally see that the others have been captured. Sonic tries to rush after them, but it was to late. When they return to Knothole, they argue about "whose fault it is" Sally insists that it was her fault, but Sonic objects. They then state they wish they could could go back in time to beat Robotnik earlier in time. Sonic remembers about a palace in the sky (which looks similar to Angel Island) that granted stones that could time travel. Sally denies this, but Sonic and Dulcy insist. With the aid of Dulcy, they head to the floating island in hopes of finding this palace. When they get there, they fight off two stone gargoyles. Sonic decides to jump off the island as an escape plan, and they both scream for help.
Dulcy hears Sonic and rescues them. However, Dulcy's poor landing skills tosses them into the palace. When they look around, they see a room with stairs constantly changing directions. They are then sucked into a room where The Keeper Of The Time Stones asks them a riddle. It is confusing, but Sally figures it out. The Keeper then gives them the Time Stones to go back in time and tells them to "synchronize your thoughts." Sally tells Sonic to focus on "Palace Fountain, 3224." However, Sonic wanders in thought for a moment about Chili dogs, but they still successfully arrive in Mobotropolis. They then see their younger selves (though not making any interaction). They then head to Sir Charles' laboratory, where they then meet their younger selves and call themselves by different names (Juice for Sonic and Alicia for Sally). They also figure out it was Sir Charles who invented the Roboticizer, and tell him about the takeover. He states that was intended to help old people live longer, but it failed, and Robotnik stole it. They then realize the date is earlier then expected meaning today is the day the takeover starts. They leave the kids with Rosie and tell her to leave to Knothole if anything happens.
Later, Young Sonic gets bored and decides to convince the other children to come to investigate. While they are looking, they get captured by Robots and are forced to surrender. Sonic and Sally go to see Sally's father, who recognizes her as her royal daughter. They tell him that Robotnik was going to take over today, but just as soon a huge blimp-like craft takes out the walls, while Robotnik evilly proclaims the kingdom his and laughs.
The time-travel mission to stop Robotnik has failed; his armies have already taken Mobotropolis! Also, Sonic and Sally have put their younger selves and the Knothole Village in the Great Forest at risk! Sonic and Sally must prevent further damage.
Antoine is sent to Robotnik's lair to obtain a message from Uncle Chuck. He is caught by a Swat-bot but is soon saved by Sonic, who complains of Antoine's foolishness. Sonic asks for the message Uncle Chuck left but Antoine reveals he did not obtain it. Sonic states that if Antoine is "so cool" he could get back to Knothole alone and runs off. Antoine is seen trembling in fear but is tapped on the back by Sonic. Sonic holds Antoine in his arms to take him back to Knothole.
Back at Knothole the following morning, Bunnie is teaching Tails martial arts. Antoine appears and asks Bunnie to teach him martial arts too. Antoine performs poorly and "ticks Sonic off" but Antoine claims he's just jealous. Antoine leaves and eventually finds the Nasty Hyenas. They announce Antoine as their king. Antoine is taken to their camp site. Sonic and the Freedom Fighters search for Antoine only to find him with the Hyenas. Antoine refuses to return and announces he has quit from the Freedom Fighters.
Most of the Freedom Fighters are asleep when Sally asks Nicole for information on the Nasty Hyenas. Nicole states that they are a group who eat their king. Antoine is seen the following morning inside a large pot being prepared to be eaten. He complains the Hyenas are using pepper on him which he dislikes and refuses to be eaten. Sonic appears and saves Antoine from the Hyenas. A Hyena sneaks up on Sonic. Antoine jumps and kicks the Hyena using the martial arts technique Bunnie taught him and they escape.
Antoine is recounting his tale and shows the kick he performed on the Hyena. Bunnie thinks he did good but he insisted on doing better. He attempts the kick again but falls on Dulcy's foot. Dulcy, in pain falls over and wrecks the house with Sonic commenting "We should've let 'em eat him".
Sonic takes Tails on a camping trip to train Tails to become a Freedom Fighter. When Sonic tells Tails a scary story, Tails get scared. Tails tells Sonic that something is out there. Later Sonic, Tails, and Antoine leave to go back to Knothole.
Dulcy is summoned to a dragon mating ground as Robotnik seeks to Roboticize the remainder of her species.
Sonic is running across the Great Unknown when the Void opens up in the ground beneath him. Using a Power Ring he manages not to be pulled in. He finds a golden artifact, which he brings back to Knothole. Sally believes it is an artifact from the Mandaras people, and intends to study it. Sonic receives a message from Uncle Chuck and leaves for Robotropolis. While he's gone, Sally discovers that the artifact may be fake, but she reads an inscription on it. Suddenly, Sally and Bunnie are engulfed in red light. They enter a trance-like state and fly off towards the Void, leaving Nicole behind.
Uncle Chuck informs Sonic about the Doomsday Project, though he doesn't yet know what it is. Sonic returns to Knothole, to find Sally gone. He asks Nicole what happened, and becomes infuriated at her technical language and inability to volunteer information without being asked. He starts shaking her until she speaks more simply. She displays an image of what happened before Sally disappeared, and says the energy resembles readings from the Void. He goes to investigate.
Snively detects Void energy, which panics Robotnik. He is terrified of the wizard Naugus, an old partner (or boss) of his whom he trapped in the Void many years ago (and who had a habit of turning his head into different animals, to Snively's obvious enjoyment). He sends his robots to close the portal. When he finds Sonic in the area, he starts worrying that his two enemies, Sonic and Naugus, might be working together. He sends the robots to destroy Sonic, and when another portal to the Void opens he forces Sonic into it.
Meanwhile, the wizard Naugus has used his magic to bring Sally and Bunnie to him, as bait for Sonic. He discovered the Void many years ago, although it was Robotnik who found the means of accessing it - and Robotnik who then trapped him inside. Naugus has since learned how to open the portal out, but can't escape without Sonic's speed. When Sonic himself arrives, Sonic has no interest in helping someone who kidnapped his friends. He takes Sally and Bunnie and tries to escape himself, but instead finds a beautiful crystal replica of Castle Acorn. And, inside, they find the King himself!
Sally is overjoyed to be reunited with her father, but he seems weak. He asks Sonic to take him out of the Void, which Sonic is only too pleased to do. However, once Sonic and the King are gone, Sally gets another surprise. Ari the ram (who was sucked into the Void previously) appears, explaining that Naugus knew Sonic wouldn't take him out, so he impersonated the King. Sonic has taken taken Naugus into the real world, and the King is still here! Sally and the King are now re-united for real.
Back in the Great Unknown, Naugus drops his disguise and freezes Sonic in crystal. When one of Robotnik's egg cameras sees them, he sends a message to Robotnik ("Wanna play?"). However, being in debt with Sonic for delivering him from the Void, Naugus releases the hedgehog, allows him to rescue his friends and the real King, and goes to confront Robotnik. The evil dictator attempts to plead for mercy (to no avail) to the evil wizard, who starts transforming Robotnik's head into many different animals, finally settling on a pig and forcing him to root around in the dirt (all of which is monitored by Snively, who laughs uncontrollably at his uncle's humiliating misfortune). Before he could continue further, Naugus is shocked to realize that his feet have turned into crystal. Realizing that he can't go any further, Naugus is forced to turn Robotnik back to normal and chases him away by saying that he's going to play 'hide and seek'. This terrifies Robotnik, who then flees away in his hovercraft with Snively.
As Sonic brings the others back to Mobius, they notice Naugus' crsytallized feet. The King instantly learned that he too is turning to crystal. Naugus explains his miscalculation: he and the King have been in the Void for far too long, and cannot survive outside, since it's drawing their lifeforce back into it. Naugus states that he can control the Void's properties, but it can be only done from within the Void itself, which means that he and the King must return back to the Void otherwise they will both die. Realizing that Naugus is right, the King gives Sally a list of the other Freedom Fighter groups in case she would need help in taking down Robotnik. After the King tells Sonic to take care of Sally, he and Naugus return back to the Void before the portal closes, both of them vowing to return one day (the King tearfully bidding farewell to Sally and Naugus angrily declaring to an absent Robotnik that he will return).
Sally cries to have been separated again from her father after such a short time. but Sonic helps her to see the upside: she did get to see him, and someday Naugus will figure a way out. Not only that, but they have the Freedom Fighter list and Ari is back. Sally has to admit that Sonic's right, as does Nicole ("He's cool, Sal. Way past."), leaving Sally to wonder just what Sonic has done to her.
During the winter in the Great Forest, Sonic and Antoine attempt to guide Dulcy down safely into Knothole in the middle of a snowstorm. Unfortunately, due to Antoine's poor air visibility, Dulcy crashes into most of the huts. Fortunately, Sonic alarms some of the in inhabitants of Knothole, who then abandon their huts before Dulcy demolishes them. Later, while Antoine is relaxing in his hut, Sonic barges in, with a suitcase full of his socks, telling him that they're going to be "roomies" until the snowstorm stops, so he can start rebuilding his hut, much to Antoine's dismay, whom faints upon hearing this news. While Antoine and Sonic are waiting out the storm, a series of vignettes occur: Antoine tries to throw Sonic's sneakers outside after seeing that they are dirty, letting snow into the hut into the process. Later, Sonic makes some chili dogs, and while getting the chili, accidentally splatters it onto Antoine's face, causing him to faint in frustration. Some time after that, after Antoine comes to, he finds that there are dirty dishes everywhere, and sees Sonic sitting at the table with his legs up, eating the last chili dog. The sight of this manages to make Antoine go a little crazy, making Sonic believe that Antoine really wanted a chili dog.
Finally, later that night, Sonic begins to "sleeprun", dreaming he is in Robotropolis facing down Robotnik. The noise caused by this wakes up Antoine, who is now at the point of a nervous breakdown. He finally snaps, deciding "if you can't beat 'em, join 'em." He then proceeds to tear up his hut. Sonic wakes up and after seeing Antoine going insane, he leaves. The noise disturbs some of the Freedom Fighters. They come to see what the source of the noise is, and narrowly avoid getting hit by one of Antoine's cushions. Sally then asks Sonic what is wrong with Antoine. Sonic states he has no idea, and states he will begin rebuilding his hut immediately, adding he has had enough of Antoine. Then a tree crashes onto Antoine's hut. But inside, the sounds of Antoine screaming and laughing maniacally continue.
Rotor builds a robot named "Ro-Becca". It was built to take orders from Rotor. When Rotor leaves Ro-Beca alone to get something he needs to help it work properly, Antoine accidentally activates it. Since Ro-Becca doesn't have everything she needs to work properly, she tries to help Antoine instead of taking orders from Rotor (which is more of an annoyance to Antoine).
Sonic and company finally make contact with another Royal Freedom Fighter group. They must work together when a nearly indestructable war-machine arrives to attack. However Sonic and the others are forced to travel through a tunnel which carries a "curse" against all intruders.
Uncle Chuck, once again spying on Dr. Robotnik, informs the Freedom Fighters of the dictator's plans on uncovering the Deep Power Stones, a source of incredible power that was hidden by the royal family in the fear it may fall into the wrong hands. It is up to Sonic and "Tails" to prevent Robotnik from getting his hands on them to power his ultimate trump card.
At a factory in Robotropolis, Uncle Chuck waits until the Swat-bots are not looking and slips away from his workplace to head up to the control room to gather more intelligence for Sonic and the Freedom Fighters, not noticing having been spotted by Snively as he made his way across the upper corridor. Once in the control room, Uncle Chuck retrieves the schematics for the robot tankers that are due to ship out soon to head for Robotnik's Project Doomsday, but before he can get the shipping schedule, he's confronted by Snively. Saying that a fuse malfunctioned and he's resetting it, Uncle Chuck leaves, but Snively is still suspicious.
A short while later, Sonic arrives at his uncle's hideout with a chili dog for him, while his uncle hands him the disk carrying the schematics on it. After revealing how Snively almost caught him, Sonic tries to convince his uncle to call it quits with his spying and return to Knothole, but Sir Charles refuses until Robotnik is defeated for good. After checking to make sure the coast is clear, Uncle Chuck has Sonic head back to Knothole with his latest intelligence.
Meanwhile, at the still under construction Project Doomsday, Robotnik checks in with Snively regarding the tankers, and asks for an update on where Snively stands with them. After Snively reports that he's ahead of schedule by a few minutes, neither realize their conversation is being picked up by Uncle Chuck at his hideout. When he learns that the tankers are shipping out in the morning, he sends word to the Freedom Fighters.
Once the Freedom Fighters learn of the tankers being sent to Project Doomsday, they set up a plan to sabotage the fuel tanks. While Sonic lures away the Swat-bot guards by playing on their programming to pursue him as top priority, Sally, Bunnie, and Antoine use special magnetic suits to cling to the underside of the tankers so they can sabotage them. Sally's suffers her suit malfunctioning when a wire comes loose, but Antoine saves her from being spotted by the remaining Swat-bot escorts until she can repair it. Meanwhile, Snively sees the pursuit of Sonic and contacts Robotnik. When Robotnik discovers the reduced escort, he orders Snicely to send the ones pursuing Sonic back to the convoy as Sonic is a diversion. When Sonic sees the Swat-bots pursuing him stop and head back, he realizes the others are in trouble. Sonic uses a Power Ring to double-time it back via the sewers. Just as Sally is sabotaging the last tank, the convoy is halted, and the Freedom Fighters are forced to surrender to the Swat-bots. However, Sonic arrives and knocks them over, buying time for the Freedom Fighters to escape back into the sewers.
At Project Doomsday, Robotnik is livid at how the Freedom Fighters have disrupted his operations at least four times within the last four weeks and wonders how they are predicting his every move. Before Snively can answer, Robotnik realizes they have a spy.Back in Knothole, Antoine is hamming it up regarding saving Sally from being discovered, but Sonic is still concerned about his uncle.
In Robotropolis, Robotnik has Snively wear a special device that prevent whatever they are saying from being picked up by the spy's equipment and orders him to conduct an electronic sweep of their headquarters. Soon, they find Uncle Chuck's bug and have a Tech-bot sabotage it, knowing that the spy will have to come to fix or replace it, then they'll have him. Meanwhile, Roter has repaired both one of Robotnik's vehicles and security transponders so they can enter Robotropilis without detection. After seeing his project, they use the transponder to find out Robonik has discovered Uncle Chuck's bug, to their horror. They send a message back telling the others about this.
What follows is where Antoine, in a bid to help Uncle Chuck, ends up being caught instead, leaving him to be tortured by Snively, forcing Sonic to save him, but protecting Uncle Chuck a little longer. However, it turns out that when the bug was discovered, Snively ordered a scan to find a match and Uncle Chuck is discovered by a Techbot. He is captured and his hideout is destroyed, which Sonic discovers upon coming back to check on him. Robotnik is stunned to see Sir Charles who Sinivley explains is the real spy, but Uncle Chuck refuses to disclose any info on Knothole. All Robotnik has to do is try to reactivate Sir Charles' Robian programming, and he'll tell Robotnik whatever he wants to know. Luckily, Sonic arrives to save his uncle before he could spill the location of Knothole to Robotnik, and after leaving Robotnik, Snively, and the Swat-bots in a whirlwind that Sonic churns up, uncle and nephew escape to regroup with Sally and Bunnie.
Sonic tells his uncle he must come back to Knothole as his cover has been blown but, having anticipated the loss of his first hideout, Uncle Chuck has another one ready and waiting to be used, and with Robotnik having seen his face, Uncle Chuck disguises himself as a Tech-bot so he can continue his spy work. After a heartfelt good-bye with Sonic, Sally, and Bunnie telling him to stay safe and how they will still miss him back in Knothole, the Freedom Fighters depart on their Hover Unit to return home, as Uncle Chuck watches them leave as a couple of tears fall from his Robian eyes.
Despite the setbacks as a result of Sir Charles sabotaging his plans by providing intelligence to the Freedom Fighters previously, Robotnik's Project Doomsday is complete and ready to become operational, with him and Snively overseeing the activation. Robotnik is convinced that once Project Doomsday is activated, all of Mobius will be his within 24 hours. With that, he activates Project Doomsday, and basks in the sound of his impending victory.
Back in Knothole, Sonic is with Rotor in his lab as he's just finished work on the first of several specially-designed water balloons loaded with a chemical capable of dissolving metal as Sonic tests it on a pile of scrap metal with one of them. After Rotor reveals that he has enough for 25 of them, Sonic leaves him to his work while he goes to check on the lookouts. He finds Antoine sleeping on the job and quickly wakes him up before saving him from a nasty fall. However, their peace is short-lived as the ground begins to split open, forcing Sonic to grab Antoine and take him to safety as one of the tubes that Project Doomsday deployed into the ground emerges and releases a Doomsday Pod from it. Sonic realizes Robotnik has tricked them and started his Doomsday Project a week early! As the Doomsday Pod begins laying waste to Knothole, Sonic has Antoine raise the alarm before going to see Rotor for one of his metal-eating balloons. However, the Doomsday Pod soon begins attacking the trees by Rotor's workshop, forcing Sonic to grab him and pull him to safety with only three of the balloons out of the 25 he made as the rest are destroyed along with Rotor's workshop when a tree trunk lands on top of it. Sonic quickly gets some payback as he uses one of the remaining balloons to destroy the Doomsday Pod.
With all of Mobius in danger, the Freedom Fighters prepare for their final battle. Sally sends messages out to summon the other Freedom Fighter leaders before she and Sonic look over the schematics for the Doomsday Project via Nicole, figuring that with hundreds of Doomsday Pods already swarming Mobius, time is critical to stop Project Doomsday before the whole planet falls under Robotnik's iron fist. Once the other Freedom Fighter leaders show up, including Ari, Lupe, Pollo and Dirk, the Freedom Fighter groups decide to infiltrate the Doomsday Machine. After Ari points out a straight assault would never get past the Swat-bot security, Sally ops for Plan B: Using hundreds of decoys to confuse the Swat-bots so they can slip in undetected. However, while Sonic, Sally, Bunnie, and Antoine make it inside using one of the remaining two metal-eating balloons, Ari, Lupe, Pollo and Dirk are captured by the Swat-bots after Robotnik takes notice and has the Swat-bots put on high alert. With the other Freedom Fighters captured, Sonic ops to go it alone while Sally, Bunnie, and Antoine retreat on one of the Doomsday Pods. Robotnik permits them to leave, only interested in Sonic, despite Snively's protests.
With Nicole's help, Sonic finds the power core and sets the charges, but when Nicole detonates them, Sonic finds the core undamaged, before Robotnik reveals he reinforced it with a special diamond-reinforced casing, and drops Sonic into a Roboticizer that Robotnik designed just for him. It looks like Robotnik has won, but Sonic manages to use three Power Rings to escape his Roboticization and flee back to Knothole, while Snively complains to himself at how Robotnik should have heeded his warnings.
Back with the Freedom Fighters, now including Tails and Uncle Chuck, it looks like Mobius is doomed, until Uncle Chuck brings up the Deep Power Stones. Sonic is concerned that is impossible since Robotnik has one of them, but Uncle Chuck convinces him to take it from him. With that advice, Sonic sneaks back into Robotropolis, and finds that the city is devoid of Swat-bots as they are all at Project Doomsday. Finding Robotnik's office, Sonic has Nicole crack the combination lock on Robotnik's safe, but unable to find the Deep Power Stone there, Sonic nearly passes it up before Nicole has him back up to find it sitting on a bookcase. With the stone secure, Sonic returns to the other Freedom Fighters, and Sally realizes they still have a chance to stop Robotnik.
Returning to Project Doomsday, Sonic tries to talk Sally out of what is about to happen, but Sally convinces him that they are in this together, no matter what happens. With that, Sonic drills his way back inside, and after using their last metal-eating balloon on a Doomsday Pod, they reach the power core and pull out the Deep Power Stones. They plan on using them like before, which would mean sacrificing themselves in the process since they have no idea how big the explosion could be, it could very well wipe out all of Mobius, until Sonic suggests putting them together the other way. As they ask Nicole about it, they are spotted by Snively, who warns Robotnik. Horrified to see that they have the Deep Power Stones, Robotnik orders all Swat-bots to the core to stop Sonic and Sally and get the Deep Power Stones. After having Nicole look over the Deep Power Stones, she reveals that if Sally and Sonic put them together the other way, the power granted to them would be equal to 10,000 Power Rings. With the fate of Mobius hanging in the balance, Sonic and Sally agree to take the risk, only to soon be surrounded by Swat-bots, demanding they turn over the Deep Power Stones. Instead of doing as they command, Sonic and Sally unite the stones together, and the power soon begins to course through their bodies. Supercharged by the Deep Power Stones, Sonic and Sally begin tearing Project Doomsday apart as the Swat-bots scatter and soon flee for their lives with Tech-bots, Robians, and Mobians joining them. Ari, Lupe, Pollo and Dirk are able to escape to a Hover Unit and flee themselves, while with his plans falling apart around him, Robotnik flees to his personal Hover Unit to escape, refusing to let Snively on by saying there's only room for one. After Robotnik flees and Snively retorts that Robotnik doesn't give him enough credit, Snively escapes himself via a hidden elevator pod that takes him underground. As Sonic and Sally continue their destruction of Project Doomsday, Robotnik voices his hatred for Sonic by saying calmly, "I really hate that hedgehog", before he snaps and rants, "I hate him! I hate him! HATE HIM!!! HATE! HATE! HATE! HAAAAAAAAAAAAAAATTTTTTTTTEEEEEEE!!!!!"
He can only groan, gasp, and shout afterwards as Project Doomsday is wiped from the face of Mobius forever, and Sonic and Sally regroup on a distant hilltop to celebrate their victory before returning to Knothole, still imbued with the energy given to them by the Deep Power Stones.
Back at Knothole, everyone celebrates after Sonic and Sally announce the defeat of Robotnik, followed by a passionate kiss between the two Freedom Fighters, setting off fireworks overhead as everyone else chants "Freedom! Freedom!"
However, Snively has survived, and he's planning to follow in Robotnik's footsteps. And to make matters worse, he's not alone...
- 26 (total)
- The Fastest Thing Alive (all episodes)
- Kappei Yamaguchi as Sonic the Hedgehog (Child & Teenager)
- Nariko Fujieda as Miles "Tails" Prower
- Yuka Shioyama as Princess Sally Acorn (Child & Teenager)
- Aya Hisakawa as "Nicole" aka Sally's Computer
- Masashi Ebara as Antoine Depardieu
- Rica Matsumoto as Bunnie Rabbot
- Mayuko Aoki as Dulcy
- Kozo Shioya as Rotor Walrus
- Toshiya Ueda as Sir Charles Hedgehog aka Uncle Chuck
- Saburo Boya as Young Antoine
- the late Takeshi Aono as King Acorn
- Ikuko Otani as Rosie
- Koichi Hashimoto as Dr. Ivo Robotnik/Dr. Eggman & SWATbots
- Hiroshi Yanaka as Snively
- Jaleel White as Sonic the Hedgehog
- Bradley Pierce as Miles "Tails" Prower
- Kate Souie as Princess Sally Acorn & Nicole
- Rob Paulsen as Antoine
- the late Christine Cavanaugh as Bunnie Rabbot
- Cree Summer as Dulcy
- Mark Ballou as Rotor the Walrus (Season 1)
- Cam Brainard as Rotor the Walrus (Season 2)
- the late William Windom as Sir Charles "Uncle Chuck" Hedgehog
- April Winchell as Rosie
- T.J Mowry as Young Sonic
- the late Dana Hill as Young Sally
- Tim Curry as King Acorn
- Jim Cummings as Dr. Robotnik
- Charlie Adler as Snively
- This Sonic cartoon is the only series that is in last place with the less most episodes. Sonic Boom is in first place with the most episodes while Sonic X is in second place whereas AoStH is in third place.
- This incarnation of Sonic the Hedgehog is Kappei Yamaguchi's final performance as the character. He also did the character's voice in Adventures of Sonic the Hedgehog.
- This is the first cartoon to feature Sonic as a young child (Blast From the Past), the second time was in Sonic Underground (Beginnings). However this cartoon was the first time that Jaleel White didn't do Sonic's voice as a child.
- The only cartoon series that Jaleel Whiterecorded his lines by himself, instead of being in the same room with the other cast members of this series.
- The show was also the partial basis for a comic book series called Sonic the Hedgehog by Archie Comics, which continues even twenty years after the cartoon's cancellation and still features many of the cartoon's own characters. Despite its cancellation and limited recent airings, the show enjoys a large and loyal internet fanbase. In response to popular demand, the entire series was released onto DVD by Shout! Factory on March 27, 2007. On February 2, 2015 the show is being shown on Netflix.
- Before this show first premiered in England, the English Sonic the Hedgehog comic (Sonic the Comic #12, 30 October 1993) showed pictures advertising a new Sonic cartoon and telling readers to watch out for it coming soon. Instead of the Freedom Fighters, the group was named the Freedom Team and consisted all the animals rescued by Sonic in Sonic the Hedgehog (1991). The members were: Sonic, Johnny Lightfoot (rabbit), Tux (penguin), Princess Acorn, Joe Sushi (walrus), Chirps (chicken), Porker Lewis (pig) and Flicky (bird). These characters were later used in all the Sonic novels released in the UK, and Johnny and Porker became part of Sonic's supporting cast in the "Sonic the Comic" stories. After radical changes to the show (basically making enormous alterations to pretty much everything in order to make it entirely different), it became this show.
- The show's first produced episode, Heads or Tails, was aired as the 13th episode and final episode of season one. This episode features a number of inconsistancies with the rest of the show, such as slightly different designs (most noticeably Rotor and Sally, the later of which using an older design), characters behaving differently, more colorful animation and the reuse of several audio tracks from Adventures of Sonic The Hedgehog.
- Two episodes were adapted for the Sonic the Hedgehog comic book series published by Archie Comics. Specifically, "Ghost Busted" was adapted in Sonic Super Special #8, and "Cry of the Wolf" was adapted in Sonic the Hedgehog #113.
- "The Adventures of Sonic the Hedgehog" was originally going to air on ABC, but ABC executives did not like that show and told DiC they had to make a different cartoon starring Sonic the Hedgehog. DiC quickly came up with this show, which premiered on ABC in fall of 1993.
- The 13 episodes from the first season of this show ran on Saturday mornings at the same time as the 65 episodes (not including the Christmas special) of Adventures of Sonic the Hedgehog were being shown during the weekdays.
- Rotor is the only character to be played by two voice actors. Mark Ballou in Season 1 and Cam Brainard in Season 2.
- Mark Ballou left the series by choice. He was asked to reprise the role for Season 2, but opted out at the last minute due to personal reasons. Cam Brainard took his place for the second season. Years after the series was cancel, Mark stated on an Internet interview that he regretted making that choice.
- Snively is shockingly the only character in the series, to retain 'pupil-less' eyes throughout both Season 1 and 2. While Sally and Bunnie who had 'pupil-less' eyes in Season 1, both acquired pupils in Season 2.
- Throughout the series, Snively went through very little changes in appearance. His gold belt buckle from Season 1, was gone in Season 2. His personality becomes much more pronounced in Season 2; while in Season 1 he was often merely in the background, obediently obeying Robotnik.
- Rotor was originally going to be named "Boomer" in the series, according to the SatAM Sonic Bible. In "Heads or Tails", his fur was purple, and he had a slightly more "goofier" attitude. In Season 1, Rotor has grayish blue fur and more rounder than his "Heads or Tails" appearance. During Season 2 his fur was dark blue, had slightly different clothing, became a secondary character, and was involved in less action/screen time. As a result, Rotor is one of the fewest characters to undergo many changes in appearance and role play.
- Robotnik's roboticised pet bird Cluck, only appeared in 9 episodes of Season 1. While he was absent and never mentioned in Season 2.
- Sonic and Sally, are the only characters that have appeared in every episode of the series.
- Writer Ben Hurst revealed that the red eyes at the end of Sonic the Hedgehog: The Doomsday Project (1994) (the final episode) actually belonged to Naugus. He explained that the plans for the third season were: Snively tries to retake control of Robotropolis, but ultimately fails. On the verge of losing it all to the Freedom Fighters, he turns to Sonic the Hedgehog: The Void (1994), where Naugus is busy torturing Robotnik. Snively frees Naugus, and in the process also frees Robotnik and King Acorn. Naugus assumes control, and starts his new command by trying to lure Sally into capture with the King as bait. Robotnik becomes Naugus' lackey. And Snively, now reduced to a simpering nobody, defects to the Freedom Fighters. Hurst went on later to say that more developments would have come along between the relationship of Sonic and Tails, coming a little closer to the game relationship it strayed so far away from. Sooner on down the line in possible future episodes we would also have learned of the origins of Robotnik and Snively including the backstory of Sally's computer Nicole.
- A third season was planned, hence the cliff hanger at the end of the series.
- Some believe that this series was based off of the long lasting Archie Sonic the Hedgehog comics. When it's the other way around, that the comic got ideas from this series when it was still in production. It takes longer to make an animated cartoon than it is in making a comic.
- Kath Soucie used her real voice when speaking as Princess Sally.
- Dulcy the dragon was added to the series during Season 2, because the show's staff wanted another heroine in the cast along with Sally and Bunnie.
- Sonic and Sally are the only characters that have appeared in every episode of the series.
- Two episodes were adapted for the Sonic the Hedgehog comic book series published by Archie Comics. Specifically, "Ghost Busted" was adapted in Sonic Super Special #8, and "Cry of the Wolf" was adapted in Sonic the Hedgehog #113.
- CASTLE THUNDER: Heard in several episodes, usually in Robotropolis.
- The Road Runner cartoons were a major influence behind the earlier series featuring the characters Scratch, Grounder and Coconuts.
- Reboot of the earlier series "The Adventures of Sonic the Hedgehog". The show was a taken in a darker direction, seeing Sonic and Princess Sally leading rebels against Dr. Robotnik and the characters of Scratch, Grounder and Coconuts from the earlier series "The Adventures of Sonic the Hedghehog" were dropped from the cartoon.
- This cartoon and Sonic Boom, are the only Sonic cartoons not to have the Chaos Emeralds involved in the storyline.
The fourth wall is broken in this series.
- At the end of "Sonic Conversion", Sonic squeezes through the black circle (which signifies the end of an episode), turns to the viewer, and says "Serious! Yeah!".
all information on the Sonic the Hedgehog (TV Series) came from http://sonic.wikia.com/wiki/Sonic_the_Hedgehog_(TV_series)