Hans Christian Andersen. "The Ugly Duckling". Good story, but the whole "It's alright because he would grow up to be pretty!" was... unfortunate. Then a conversation on this very wiki pointed out that ducks were quite cute, and it was a matter of opinion. I also looked up baby swans (they're technically cygnets). They're really cute. The point wasn't that the "duckling" grew up and became beautiful, it was that the swan, with the benefit of looking like what he was, found people who accepted him.
In other words, the ugly duckling is one of the oldest examples of Hollywood Homely.
Also, while cygnets and ducklings do look virtually the same, except for the colour scheme, there is also presumably a difference in size: given how much larger swans are than ducks, it isn't too far-fetched to think that carries on already to cygnets and ducklings, which would make the cygnet look very much out of place. This Troper remembers seeing several illustrated versions of the tale drawing the cygnet almost twice as big as the ducklings.
Do We Have This One? The problem is that the cygnet kept judging himself by what he wasn't until he discovered what he actually was. Seen as a duckling, he was ugly; seen as a cygnet, he is beautiful. The point is, don't try to ram a square peg in a round hole - go look for a square hole.
Gee, given how ferocious swans are, the "ugly duckling" would be perfectly able to heap retribution on those who tormented him growing up. I can see it now: "Revenge of the Ugly Duckling" With the tagline: They tormented him as a cygnet...and now they will pay.