Vanessa

Vanessa is Ursula's human alter ego from The Little Mermaid. She is an extremely beautiful woman who brainwashes Prince Eric into loving her instead of Ariel.

Personality
Because of her very brief appearance, her personality was not fleshed out much, but a few details were apparent. Ursula, while in this form, sheds most of her diva personality and acts more spritely when alone, but puts on a convincing facade of innocence when around others. Vanessa acts much like the valuing of the 'body language' that Ursula talks about, by wearing more revealing outfits than Ariel would, while snuggling Eric sensually. The only times she talks much are either alone, or when under attack, when she will scream in despair, or yell in anger. Despite this, she is not entirely defenseless; when pushed she will begin to fight back brutally, as seen when she choked Scuttle (and when it's implied that she smacked around the other birds).

She has a very strong resemblance to Ariel, with a few notable differences: her hair, eye color and shape, skin tone, and a slightly thinner hourglass shaped body. It's is very likely that Ursula did that on purpose in order to make it more believable that she was the one who saved Eric, while keeping Ariel from figuring out her true identity.

Ablitlies
Vanessa was capable of hypnotizing people with her (actually Ariel's) voice, and can do so so long as her nautilus survives. Presumably, she was also either a skilled swimmer or possessed teleportation abilities, as evidenced by her arrival at Prince Eric's castle from Ursula's grotto. She also has limited shapeshifting capabilities, which are strengthened with the nautilus.

Presumably, she also has the same abilities as Ursula, although it is not made clear either way if she does.

It's also implied that she was capable of summoning a storm when she needs to even without the nautilus, as evidenced by a storm immediately appearing the second the sunset ended on the third day, and her utilizing it to transform back into Ursula.

The Little Mermaid
When Ariel comes "too close" to succeeding in her task, Ursula takes the form of a beautiful woman with Ariel's voice in order to sabotage her relationship with Eric. Ursula adopts the name of "Vanessa", and when in this form, her voice is provided by Jodi Benson, who also voices Ariel. The concept of the beautiful dark-haired rival for the prince's affections is another plot point adapted and modified from the original fairytale.

Ursula as Vanessa bewitches Eric to marry her by brainwashing him with a flowing trail of Ariel's stolen voice. She sadistically makes certain that Ariel sees her snuggling and clinging to Eric rubbing and pressing her feminine curves against Eric's torso. However, Scuttle manages to discover her true identity while she is maniacally gloating about her inevitable victory via her reflection. The wedding is disrupted before they could exchange their wedding vows. Vanessa gets attacked by all sorts of animals: Scuttle leads birds to divebomb her before finally flying through her skirt, pelicans drop dead fish and cold sea water on her drenching her from head to toe. A lobster, dropped by one of the pelicans, gets stuck in her veil and pinches her nose and she screams before countless starfish coat themselves across her torso from the waist up including her screaming mouth. She pulls the starfish off of her face and another one from her shoulder but seals start bouncing her up and down before throwing her into the wedding cake destroying it and the table. She angrily crawls out from the ruin, covered in icing when a pod dolphins spit water on her, and finally Scuttle screams in her face. She angrily tries to choke Scuttle, only for Eric's sheepdog, Max, to take an enormous bite out of her butt. At the last minute and the nautilus shell containing Ariel's voice is broken, breaking the enchantment and returning Ariel's voice back to its owner. In the course of this physical assault Vanessa's public facade of innocence gradually, but quickly, disappears as the increasingly flustered bride becomes vicious and shrill in her attempts to defend herself. Unfortunately, in spite of this, Vanessa/Ursula nonetheless succeeded in winning the deal, and Vanessa unleashes her true form of Ursula in front of the guests by terrifying them.

House of Mouse
Ursula briefly appeared as Vanessa once on House of Mouse in the episode "House of Crime". Goofy interrogates her, asking if she has seen any disguised villains. She pretentiously answers no, and then transforms back into Ursula when Goofy leaves her table.

Kingdom of Hearts 2
Vanessa had a brief appearance in Kingdom Hearts II, where, in a similar fashion to the movie, she manages to brainwash Prince Eric. However, they apparently do not wed in Kingdom Hearts, as Sora discovers her and Eric walking down the beach nearing the sunset of the third day without any of them wearing their wedding garments. Flounder instantly identifies Vanessa as being Ursula when he notices the nautilus necklace on her, causing Sora to destroy the necklace by firing a beam from his Keyblade. While walking down the beach, Vanessa sings a very similar song to what Ariel sang to Eric in the movie after saving him the first time.

Knownable Relatives
Ursula  (after ego)

Morgana (sister)

Trivia

 * The name of Ursula's human disguise, "Vanessa", is derived from the Latin word "Vanitas", meaning "Vanity," "Worthlessness," "Emptiness," and "Nothingness." Interestingly enough, a character named Vanitas appears as one of the main villains of Kingdom Hearts Birth by Sleep, but unrelated to Ursula.
 * In the original draft for The Little Mermaid, Vanessa's role in the plot was quite different than in the final version. Originally, Eric proposed to Vanessa willingly after he discovered that she had the voice he was looking for, although he later had second thoughts at the actual wedding, when Vanessa intimidated him into saying "I do." Also, Vanessa was originally supposed to wear a scarf in order to ensure that her identity as Ursula was safe (as it hid her nautilus) when meeting people up close (such as Ariel). The attack on her was actually much different in the original version, as Scuttle and the various aquatic fauna did not start attacking her and the ship until just before the priest could pronounce them Husband and Wife. While fighting off the animals, Vanessa also nearly hinted that she wasn't who she claimed she was so she faked fear at a suspicious Eric. Scuttle, in this version, also decided to exploit the fact that Vanessa's true form can be revealed from her reflection by airlifting the mirror from the bridesroom over to her and positioning it near her, but she caught on and destroyed it before he could get into position. However, her reflection was already exposed from water seeping onto the deck from the animals, thus giving away who she really was to Eric. Perhaps the biggest difference is that Vanessa still kept Ariel's voice, though for some reason, she was unable to use it anymore.
 * At one point while Vanessa was being harassed by Scuttle, she yells angrily "Oh why you little!" and strangles Scuttle in a very similar manner to Homer and Bart in The Simpsons. (Coincidentally, both The Little Mermaid and the first Simpsons full length episode were released in 1989)
 * Her name is never revealed in the film before the wedding, often in storybooks she is known as The Maiden.
 * In concept arts of Vanessa which is shown on DVDs of The Little Mermaid, her name was written with an 'E', but apparently there was confusion amongst the movie staff, causing her name to appear with an 'A' on her production cel, and everything afterwards.
 * Vanessa is one of four characters to possess violet eyes, the other three being Aurona,Megara and Doctor Facilier. On a related note, Vanessa was also the first villain to possess violet eyes, eventually being succeeded by Facilier.
 * In the official comic adaptation, Vanessa was shown multiple times singing in Ariel's voice without the necklace hanging around her neck, implying that so long as the necklace is safe, she will be able to speak with Ariel's voice.
 * Vanessa speaks only twice during her brief appearance with Ariel's voice exlcuding her song. When she has Ariel's voice she first screams, "Get away from me you slimy little-" and later "Oh Why You Little". Following the loss of her necklace Pat Carrol the voice of Ursula does the voice of Vanessa where she says "Eric get away from her", "Eric No!" and "You're too Late!"
 * The song Vanessa sings in her room may have been the inspiration for the song This Day Aria from My Little Pony Friendship is Magic, were the villain also sings into a mirror well she is in disguise just before her marriage to a hypnotized man.

Voice Actresses
Japanese :

English : Jodi Beson (Ariel's voice/Singing voice), Pat Carroll (Ursula's voice)