Hoist by Her Own Petard: She decides that it's best for Melody's safety to keep Melody ignorant of her true origins and heritage. But Melody's ignorance (and Ariel's unwillingness to be truthful when she finds the locket) is exactly what causes her to run away and go against her mother until Morgana reveals her true colors.
In the TV series episode "Scuttle", Eric catches a brief glimpse at Ariel, but is convinced by Grimsby that it was just his imagination.
Friend to All Living Things: He helped free a dolphin from a net. Unbeknownst to him, his future wife, Ariel watched him save the dolphin. While she doesn't see his full face, Eric's selfless action was the catalyst that helped Ariel to believe that not all humans are evil.
Then, there's his brotherly and close relationship with Max his sheep dog.
Love at First Note: While he does see Ariel for a couple of seconds, due to complications involved with being half-unconscious, he didn't remember what she looked like, which lead to him falling in love with her voice.
Magical Flutist: Averted. Eric is shown to be an expert on the flute, but has no magical properties in his skills.
Attack of the 50-Foot Whatever: One episode of the series has him wish to be bigger, problem? He doesn't stop growing until he's twice the size of a large vessel, gets even worse when Ariel uses her wish for him to be "His old self" which makes him giant AND elderly.
Deadpan Snarker: Shows shades of this in the sequel. Mostly towards Scuttle.
Freudian Excuse: Implied. In the prequel Flounder was more adventurous and outgoing; a stark contrast to the first movie. It can be reasoned that he became more nervous and cautious when he befriended Ariel.
Expy: His body type and the way he walks and runs bears a strong resemblance to The Colonel from OneHundredAndOneDalmatians. Minus the talking and that Max has grey and white fur, while The Colonel has brown.
Berserk Button: Implied. When she was being reprimanded by her mother for going out into the sea, disobeying her rules. Notice that Melody didn't say anything and just took it. But when Ariel call the sea "dangerous", it's only then that Melody yells back.
Be Yourself: The lesson Melody learns a the end of the movie.
Melody: I just wanted to be a better mermaid than a girl.
Contrasting Sequel Main Character: Ariel is a mermaid who's obsessed with the land and wants to become human, while her daughter, the main character of the sequel, is a human but is drawn to the ocean and wants to be a mermaid. They're not strikingly different in temperament, but their goals are complete opposites.
Deal with the Devil: When she trades Triton's trident to Morgana in the second movie in order to become a permanent mermaid.
Nice Job Breaking It, Hero: In the sequel when she gives the Trident to Morgana, when she had the choice to give it to Ariel. Had she given the trident to Ariel, then all problems would have been solved.
Voiced by: Pat Carroll (and Jodi Benson while in disguise)
Adaptational Villainy: In the fairy tale, the sea witch was a neutral character who in addition to warning the mermaid of the transformation's consequences, didn't go back on her deal with the mermaid until asked to, and never interferes directly.
Dangerously Genre Savvy: She takes the one thing that would make Eric fall in love with Ariel (her voice), gives her a three day time limit to get him to fall for her, makes sure that the best opportunity for them to kiss is ruined, and shapeshifts into a temptress using Ariel's voice to make Eric fall for her instead.
The Dreaded: Almost every creature of the sea is terrified of Ursula.
Ink-Suit Actor: Subversion; Ursula was actually based on the drag queen Divine, who was originally supposed to voice her, but died before he could even record the voice, so the role went to Pat Carroll instead.
Ironically, in the Latin American Spanish dub, she was voiced by an actual drag queen.
Kaiju: Grows into the size of one at the final battle
Mama Bear: Ursula did not take kindly to Flotsam and Jetsam getting blasted by the trident.
Oh Crap: "Vanessa" does one when she sees the whole flock of birds flying towards her.Ursula has one in her giant form,when she's about to kill Ariel, she turns aside a bit only to see Eric charging at her in the ship and impaling her.
One-Winged Angel: Grows into a giant enemy monster version of herself at the film's climax using the trident's magic.
Palette Swap: Vanessa's appearance is basically Ariel with the hair and eye colors changed.
Sanity Slippage: She becomes more and more deranged as her plan achieves more success. By the time she's got the trident in her hands and transforms into a giant monster, the little sanity she had is completely gone.
Driven by Envy: Implied. She wanted to steal the trident not only for ultimate power, but also to prove she was better than her sister.
Even Evil Has Loved Ones: Subverted. In her first scene she appeared generally upset about what happened to her sister. Then, it was revealed it was just a façade and she actually loathed her sister.
Expy: A possibl coincidence of her similar appearance to Cruella De Vil from 101 Dalmatians.
Foil: To Ursula. In regards to body types, Ursula was obese while Morgana is quite skinny and almost skeletal. Morgana was The Unfavorite to their mother who doted on Ursula. Ursula was completely full of herself and had loyal henchmen who served her quite well, while Morgana is frequently bickering with Undertow and suffers from a major inferiority complex. Her magic is also not as strong as Ursula's. Ursula came across as more businesslike and ultimately pressured Ariel into signing her contract, while Morgana was more informal and managed to convince Melody she was truly sympathetic to her plight. Ursula indirectly used Ariel to get Triton's crown and trident, Morgana managed to trick Melody into stealing it for her.
Ambition Is Evil: A rather unusual case in that she has no interest in replacing the figurehead, just being the attaché. She's also not "evil" per se, certainly nowhere near Ursula, but her ambition is portrayed negatively because Sebastian is a "sympatheticcharacter" that's going to lose his job. It also is not promenient until the crab begins outright berating her.
Tsundere: Type 2. The "tsun" part is mostly seen when Louis acts up.
Voiced by: Rene Auberjonois
Anti-Villain: While Louis may not harbor any malice, we the viewers are aware he was preparing possibly SENTIENT sea life, this is especially apparent whenever he and Sebastian face off. Though in his case as mentioned below, it may be just a matter of pride than to actually serve the little crab up on a platter.