Continuity mistake: When Max is running out of the school after successfully becoming cool. We see his friend with the orange mohawk at least twice. Once hanging from a statue, and another where he's reaching out from a school bus. These two shots are really close together so there is no way that he could have moved that quick.
Continuity mistake: After Fritz shoves too many nuts in the Nutcracker's mouth and breaks his teeth, he gives it back to Marie and she cries out, "now you can't have him!", in this shot only a few teeth are missing. About 1 from the top row, and 1 or 2 from the bottom row. After the shot of Fritz saying, "will I ever survive?" in a very sarcastic manner, it cuts back to Marie with the Nutcracker, and suddenly a lot more teeth are missing. About 2 or 3 from the top row, and 4 or so from the bottom row, and they are more spread out in the bottom row.
Continuity mistake: In the lunchroom when the boy gets tripped, a bunch of the food flies out of the bowl in the slow motion shot. When the bowl lands on Steve Guttenberg's head, it's full of food.
Continuity mistake: When Angus and Yellow reach the lake, Angus's face is tore up pretty bad, but after they cross the lake and go to the building on top of the mountain his face is almost completely free of any injuries.