Trivia: When King Triton enters the concert hall and passes over the audience, you can see Mickey Mouse, Goofy and Donald Duck sitting among the audience. (00:03:33)
Trivia: When Scuttle discovers that Vanessa is actually Ursula, he sees Vanessa's true image reflected in the mirror, but the image we see in the mirror is not reversed, note Ursula's mole and her shell necklace are not backwards. This may be part of Ursula's magic, or simply an animation error, which is common (I believe it's the latter). (01:06:40)
Trivia: In the song "Poor Unfortunate Souls" during the line "and she who holds her tongue will get a man", we see Ursula throw an actual tongue into the cauldron. This might be a reference to the original story by Hans Christian Anderson where instead of the sea witch taking the mermaid's voice, she took her tongue instead.