* HollywoodHomely: Baby swans are more or less identical to ducklings except for feather color.
** It's probably more a case of "beauty is in the eye of the beholder" since the other ducks still shun the titular ugly "duckling".
*** Interestingly, in some versions where the old woman briefly takes him in, she comments on his ugliness, as well.
* UnfortunateImplications: The only real reason the cygnet is considered beautiful at the end is because it looks like all the other swans, while originally it was mocked by the other ducklings because it didn't look like them. There's "Beauty is in the eye of the beholder," but there's also "You're only beautiful if you look like everyone else."
* TheWoobie: The title character. Seriously, who didn't want to hug the poor little guy.