Gabriella, a deaf mermaid who used sign language (her octopus sidekick served as a translator) and appeared in two episodes. Fans love her, not just for being adorable but also for being an example of positive representation in a kids' show.
Evil Manta, for being a genuinely intimidating villain and voiced by the always entertaining and charismatic Tim Curry.
Heartwarming in Hindsight: Ursula not being as much of a Benevolent Boss to Flotsam and Jetsam in the prequel TV series as she was in the original movie may imply that she's gotten closer to them as time progressed.
Realism-Induced Horror: The episode "Giggles" is about Ariel being inflicted with curse that causes sea quakes any time she laughs. The other characters don't know about the curse, so they just see a formerly sociable and energetic teenager becoming depressed and withdrawing from her friends and family for no apparent reason. Without knowing about the curse, Ariel's behavior in this episode is a textbook warning sign of a minor being abused.
The Evil Manta. He was at first set up as the main villain of the animated series instead of Ursula, since the series takes place before the movie, and it would make a lot less sense for Ariel to make that deal with Ursula if she had already faced and fought against her before their first meeting in the movie. Only, after a while, Ursula did appear in the series, after which Manta only appeared in one more episode. Plus the possibility of him being the villain of the sequel instead of "Ursula's crazy sister".
Ariel's sisters. The nature of the show gave plenty of opportunity to explore their characters, but only two of them, Alana and Arista, ever got a Day in the Limelight.
They Wasted a Perfectly Good Plot: The Season 2 finale "T'ank You For Dat, Ariel" has Ariel temporarily gaining the powers of a sea witch and using this power to turn Sebastian into a giant crab. Ariel gaining powers could have easily been a great story in its own right, with her causing chaos as she struggles to adapt to her new abilities, and even possibly facing off against Ursula (who is completely absent). Instead, Ariel loses the power almost immediately, and hijinks with Sebastian's size take up the rest of the episode.
Villain Decay: Though not for lack of trying, Ursula was never quite as menacing in the show as she was in the movie. The only time she was about to cross the Moral Event Horizon was when she tried to kill the harmless "bad-luck creature" from the episode "Against the Tide". Unlike some cases, this can be justified as the series takes place before the movie, creating the justifiable reason that Ursula hasn't reached the same level of villainy as she has no reason to go that far yet.
The Woobie: The "bad luck creature" from the episode "Against the Tide", who only wants to find a friend yet is reviled and feared by everyone except Ariel. The fact that she cries out of pure anguish in several scenes makes it even more heartbreaking. It becomes even worse in hindsight when the ending reveals that she was pregnant and was looking for a safe place to raise her children.
