These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Adaptation Displacement: The movie, despite not being very well known, is still more well-known than the television series. It doesn't help that it's the only part of the series that was released on VHS and DVD (Aside from the series premiere episode included on the DVD as a bonus).
Family-Unfriendly Aesop: In the movie. If you have finally found yourself comfortable with your own identity but your friends don't like you for who you are anymore, it's better to go back to the way they wanted you to be. If you think of the show as a metaphor for Transsexuals, it's a pretty bad message.
Also in the movie, one of the lines in "Proud to Be a Dog" when mentioning that everything needs something else, with one of them being "Or a princess, a frog". When this line is sung, it shows Cinderella about to kiss a frog, which never happened in Cinderella. Five years later, The Princess and the Frog was released.
Hollywood Homely: Apparently, Leonard is viewed as being ugly to some of the other kids. Though aside from having a chubbier build, he doesn't look much different from the others.