Anvilicious: Andersen had the mermaid transfigured into a daughter of the air, who after three hundred years of good deeds can go to heaven. Then he re-revised it, so it's not her good deeds that earn her a soul — it's yours! — every child listening to the story. P.L. Travers snapped at Andersen in one of her folklore essays: "'But a year taken off when a child behaves and a tear shed and a day added whenever a child is naughty? Andersen, this is blackmail. And the children know it and say nothing. There's magnanimity for you."
Fanon Discontinuity: The various endings. Readers and scholars prefer the mermaid being changed into foam and dying tragedy rather than the mermaid being changed into a daughter of the air with a chance at Heaven ending.
Values Dissonance: Modern readers often have trouble with the story's moral of "Even heathens can reach salvation if they suffer enough."
The Woobie: Dear God, Hans, how much does this poor girl have to go through? For the crime of being born a fay being rather than an oh-so-lucky human, she has to suffer endless pain, have her tongue cut out, commit suicide, and then hope that no child cries or is naughty for 300 years straight before she can get into heaven?
Alternate Aesop Interpretation: The film doesn't necessarily have An Aesop - but it's been argued that the story is really a cautionary tale for parents. Triton is pretty applicable to the standard overprotective parent that goes too far and unwittingly sends his child into the arms of someone who wants to hurt and exploit her.
Applicability: Ariel's main motivation for becoming a human. While both her interests in human culture and Eric are reasons why she became a human, it's a matter of debate as to which one was the bigger motivation for her. It's also been argued that Ariel's becoming human can be seen as a metaphor for a transgender woman transitioning. She always wanted to join the human world (metaphor for transitioning), as she sings "Part of Your World" before she meets Eric. Then when she meets Eric, she decides to transition then so she can be with him - she always wanted to eventually, the prospect of getting a boyfriend just gave her the final push, as is the case with some transgender women. So Ariel gets legs and, one can assume, what goes between them. And the scene right afterward where she goes to the surface and gasps for air is rather orgasmic - as a transgender woman might try out her new parts. Also there is the rejection by and later reconciliation with her father, as a coming-out story might have. Check out some more info here.
Is Ariel a good character/role model or a terrible one?
King Triton. A well-meaning father who only wants what's best for Ariel, or a idiotic and possibly racist Jerkass father who doesn't handle Ariel's fascination with humans tactfully and brought the events of the second half of the movie upon himself because he couldn't hold his temper?
Draco in Leather Pants: Ursula gets this sometimes. You can see comments on Youtube videos taking about how she clearly explained the deal to Ariel, and how Ariel was stupid for taking it. While Ariel was being naive (if reluctant), fans are forgetting that Ursula's goal was to rule the ocean. This is also forgetting that Ursula's raison d'etre is to catch people at the very moment when they're prone to making rash decisions — and then, if it looks like they might win out, she's not above actively sabotaging their deal.
Sebastian was so popular that voice actor Samuel E. Wright recorded two albums as the character. There was even a tie-in Disney Channel special, and the character also starred in his own shorts on the short-lived Saturday Morning CartoonRaw Toonage, along with his nemesis Louis.
"Vanessa" (Ursula's disguised form) is really popular with some fans.
Epileptic Trees: In The Da Vinci Code, author Dan Brown puts forth the theory that the directors and animators were pagan goddess worshipers and scattered clues and obscure references to the "Sacred Feminine" throughout the film, including Ariel's red hair. The reality is far less mystical though: the animators chose to make Ariel a redhead to avoid comparisons with Daryl Hannah's blonde mermaid character from Splash, and also because it gave a nice contrast with the blue sea and her green tail.
Evil Is Sexy: Ursula in her Vanessa status. Some viewers found Ursula sexy even in her original form. "Don't underestimate the importance of BODY LANGUAGE!".
Fair for Its Day: Today this movie is considered by some to be rather cringeworthy, as its heroine is a girl who abandons her family and her home for a guy she hardly knows. At the time though, Ariel was written by Disney to be a proactive girl, following after the more passive and demure Snow White, Cinderella, and Aurora. She also was the first Disney princess to set out and win the heart of the guy she loved, rather than have him show up and carry her off. (And she was also the first Disney princess to save the life of her prince, twice.)
Fanon: Despite the fact that it was scrapped for the final film, many fans still write Ursula as Triton's sister.
In the original Hans Christian Andersen book, the mermaid had to earn an immortal soul at the end where she previously had none, and nowadays it is often joked that gingers have no soul. Consider Ariel's hair color in the Disney adaptation.
Vanessa, a villainous split personality of Ursula, is voiced by Jodi Benson. In the English dub of Grandia II, Jodi Benson voices Millenia, a villainous split personality.
Ariel was modelled after actress Alyssa Milano. Years later, Milano's character on Charmed would be turned into a mermaid - in a plot that heavily references this film. To make it even more hilarious, Milano is terrified of water (and shooting the underwater scenes were very tricky for her).
The Little Mermaid used the Can-Can when Louis is chasing Sebastian, and that wasn't the only landmark release in 1989 to use that. Super Mario had it for invincibility on his debut Game Boy game, which had an underwater level.
Ariel Needs Legs, a Stylistic Suck comic in which Ursula gives Ariel eight legs and Eric is a Pokémon fan. Perhaps the most well-known part is when Eric comes clean to Grimsby about Ariel's condition:
Eric: Eight legs!
Grimsby: Seven vaganias [sic].
Moral Event Horizon: Ursula starts well over the line and really crosses when she interferes with her own deal with Ariel and hypnotizes Eric into falling in love with her in disguise. It gets worse when she attempts to blast Ariel with the trident, after turning into a giant version of herself. Also in the TV series, she attempts to murder an alleged bad-luck creature despite it being completely harmless to begin with.
Narm: The scene where Sebastian has his Heel Realization and agrees to help Ariel find Eric, is a fairly heartwarming moment.... but when you remember that Ariel is essentially standing there mostly naked, the scene does come off as seeming a bit silly.
Never Live It Down: Ariel is frequently criticised for entering the deal with Ursula. A lot of the criticisms miss the fact that the film portrays it as a bad thing - and there's emphasis on the fact that Ursula is waiting until Ariel is prone to making a rash decision to strike.
Ron the Death Eater: Being on two opposing sides of an issue, both Ariel and King Triton have people who ignore all faults in one while demonizing the other.
Seinfeld Is Unfunny: The movie seems a bit like a paint-by-numbers Disney flick these days. Literally everything about it was new and groundbreaking at the time. Merging a fairy tale with Broadway elements? This was the first film to really popularize that formula. So numerous animated films these days owe their existence to this one. Another element from this one, that its successor Beauty and the Beast missed: the musical elements were sort of justified in-universe: one of the main characters is a concert composer and Ariel's singing voice is a plot point. Ursula also delivers a very theatre-inspired monologue in her first scenes, something which the later Disney villains didn't do.
The scene of Ariel finishing her "I Want" Song reprise, which shows her singing on a boulder while a wave crashes behind her in the background, is almost always the one scene that you will see in Disney's advertising and commercial spots that mention this movie.
The underwater musical in "Under the Sea" may be another one. Particularly the shot of the little sea horses swimming up around Ariel at the end are put in many generic Disney-referring clips.
There's a third one, the one in which Ariel rises from the ocean after being turned human by Ursula.
Signature Song: "Under the Sea" with "Part of Your World" also a contender.
Squick: Ursula. All the time. Especially when talking to Ariel and performing a lot of giggling like a Burlesque entertainer.
Triton is an intolerant Jerkass telling Ariel how cruel and evil humans are, since Ariel's idealistic views all turn out to be right. (Though through Moral Luck—neither had any way of knowing their view of humans was the right one based on the limited information they had at the time, living under the sea.) However, humans do catch and eat fish, which are 100% sentient in this mythos. Of course, humans don't realize that (despite Eric apparently being able to hear Sebastian naming Ariel just fine), and Triton destroying all of Ariel's stuff to try to force her to stay away from humans was still wrong (and, in some cases, illegal). The Carnivore Confusion doesn't help matters much - in real life, fish eat other fish all the time!
On a lesser note, Triton and Sebastian scolding Ariel for missing the concert. Based on Flounder's reaction, it seems the audience is supposed to think they shouldn't reprimand her at all ("But it wasn't her fault!"). However, this is far from Ariel's first no-show (as Sebastian noted earlier, "If only she'd show up for rehearsal once in a while," and Triton's "I just don't know what we're going to do with you, young lady"), and they have a point that because of her absence, the concert was ruined and those in it were humiliated. While Triton and Sebastian are too hard on her and won't hear her out, they have every right to be angry and hold her accountable for her actions.
Superlative Dubbing: Ariel's stunning Norwegian voice done by Sissel Kyrkjebø gained a lot of attention, to the point she went on to voice Ariel in the Danish and Swedish dubs as well. To further exemplify the beauty of Sissel's voice, she's also the One-Woman Wail you hear on the Titanic soundtrack.
Pay close attention to Louis the chef's ditty "Le Poisson", which has the same melody as "Be Our Guest".
They Wasted a Perfectly Good Plot: The film doesn't even bother to delve into Ariel's character at the third arc of the movie and how the experience has changed her. One of the most criticized aspect of the movie about her shallowness could have easily been fixed by showing how sorry she was at her action that almost cost Triton his kingdom.
A scene where Ariel apologises to Triton after Ursula's defeat was storyboarded, but deleted from the finished film.
There is a moment where she tells Triton that she's sorry and didn't know what she was getting herself into...but it sounds less like a sincere apology and more like she's trying to get out of trouble.
What Measure Is a Non-Badass?: People love to throw up the "Ariel is a stupid bitch and a bad role model for little girls who THROWS HER LIFE AWAY FOR A GUY" pseudo-reason, without bothering to dwell into her reasons and psyche (she already wanted to see the human world, Eric was mostly the push she needed to take the decision to go there, etc). Apparently a woman isn't allowed to fall in romantic love ever, specially if it's a teenage girl with next-to-none real life experience!
What an Idiot: Ariel somehow forgetting the concert was that day is a little believable. What raises eyebrows however is that none of the other concert personnel reminded her at all. Or that her sisters - who are visibly shocked that Ariel isn't there - didn't at least check to make sure she was in her position on the stage. Sebastian really deserved the embarrassment he got for allowing such a mistake to happen.
The Woobie: Ariel is really good at looking like a kicked puppy.
Falling into the Jerkass Woobie category is Triton. Yes, he holds some pretty racist views in regards to humans and arguably goes way too far in punishing Ariel by destroying her collection. However, when he finally realizes what a terrible mistake he's made, Ariel is already gone and there's no sign of her.
Undertow from the sequel. With Melody being a copy of her mother, Morgana and her sting rays being copies of Ursula, Flotsam, and Jetsam, and Tip and Dash being copies of...Timon and Pumbaa, Undertow is the only new character with some originality. Doesn't hurt that he's voiced by Clancy Brown.
Benjamin from the prequel. While the movie doesn't sit too well with the fans most agree that he is its saving grace, being an Ambiguously Gay and yet still very cute manatee.
Gabriella in tv series, 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.
"Funny Aneurysm" Moment/Harsher in Hindsight: In-universe example: In the episode "Metal Fish", Ariel saves Hans Christian Andersen, and it is heavily implied that he ended up writing the story in honor of her saving him. Said story ended up published a year later in the story, and given what happened to the character based on her, it's unlikely that Andersen was too happy that Ariel married Eric.
Magnificent Bastard: The Evil Manta from the series, who manages to turn the different species of the entire kingdom against each other in his debut episode. Not only that, he also tricked Ariel into setting him free to begin with. Oh, and he's voiced by Tim Curry, no less. Though his fourth and final appearance puts him through Badass and Villain Decay; suddenly he's a father, Tim Curry voices him a lot less creepily, and he ends up with some redeeming qualities.
Ron the Death Eater: Ariel also gets some of this in regards to her parenting towards Melody in the sequel. Many fans are a little too eager to sham her by calling her a hypocrite because of how overprotective she was of Melody, ignoring that Ariel did try to keep Melody from making the same mistakes she did. Also that Triton was being paranoid about humans in general when he tried to keep Ariel safe, while Ariel was trying to protect Melody from a definite threat in Morgana. (Although it doesn't help that Ariel doesn't sit Melody down and explain what the "definite threat" is, but simply tells her to stay away from the ocean because "it's dangerous," when she herself understandably didn't believe her father when he said to stay away from the surface because "humans are dangerous.")
Also bordering with a major case of It Runs in the Family and Adult Fear: Triton may have been paranoid, but his heart was in the right place, and he proved to love her daughter so much to sacrifice everything, including himself, to keep her safe and happy. Exactly what Ariel did: she just needed to be a mother herself to understand how hard is being a parent.
Strawman Has a Point: Triton has even more of a point if you've seen Ariel's Beginning and consider it to be canon. Ariel's mother was killed when human fishermen came to steal mermaid relics and accidentally(?) rammed their boat into her. Even if Triton accepted her passing in the end, that doesn't necessarily mean that he thinks highly of humans. It's no wonder he doesn't like humans—they killed his wife!
They Wasted a Perfectly Good Character: 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".
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.
King Triton in Ariel's Beginning. The guy lost his wife Athena in a pirate attack, and many years later he still can't listen to music without being reminded of that tragic happening. Through the whole movie he looks so sad and depressed of what he had lost, and his strained relationship with Ariel ain't helping him.
*It gets worse: by the first movie, his relationship with Ariel is so damaged that she prefers trying her luck with Ursula than trusting him again, he's visibly distraught and blaming himself for her escape and, when finally after years of bickering manages to patch his relationship with his daughter, he's grimly reminded that Ariel forgave him at her own marriage. When he realizes that he's going to miss her, he also realizes that now Ariel has her own family to care for, and he can never, ever get back the time they spent bickering. And then, in the second movie, we find out that he didn't even get to be a grandfather for his (possibly) first granddaughter.
Melody in the sequel after being humiliated at her birthday party.