Other mistake: In the scene where Drakken accidentally "clones" Bonnie Rockwaller instead of Kim Possible, he holds up a picture of Kim to compare the results of his experiment with the real thing. The Bonnie clone, completely encapsulated behind the glass of Drakken's cloning machine (as evidenced by the reflection of light off of it) somehow manages to get a hold of the picture despite this barrier. (She does this without having to break the glass.).
Other mistake: Often, when Sakura is about to punch Naruto, he has enough time to dodge her attack but never does it.