I'd slightly tweak this and say that people who know physics are perfectly capable of enjoying silly sci-fi because they don't take it seriously.
So, are you saying the movie's meant to be similar to a cartoon simply because it's a movie that's largely for laughs? That there was no need to bring more accuracy than necessary to a movie made for the family?
I don't know. I mean, justifying that kind of behavior would be more fit for a parody. But when I started this thread I was afraid I was reading too much into it.