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: When the father pulls the cover off the toy castle that's Drosselmeier's gift to Marie and Fritz, there are no soldiers visible in or on any of the towers. But when there is a close up of Marie asking how Drosselmeier got in, there is a soldier on the tower next to her head. Then the camera cuts to a different angle as Drosselmeier approaches and the same tower is visible, but with no soldier.
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.