Most significantly: they "borrowed" their robot monster design from an old "Jonny Quest" episode. That wasn't a "based on" or "inspired by" thing. That was a rip off. If I were Hannah-Barbera, I'd be looking for remuneration on that one.
Mostly, though, it was just disappointing because it wasn't nearly as funny as everybody says it was. Two or three laughs do not a funny movie make. People set their sights so low these days.