Revealing mistake: After Littlefoot and Cera's fight, Cera's dad says that each herd is on its own. This shocks the little dinosaurs and they gasp. Notice in this shot that though the dinosaurs move, their shadows don't. Petrie doesn't even have a shadow.
Revealing mistake: At the concert, when the hecklers are throwing the cups and cans at the crowd, and the crowd are doing the same thing to the hecklers, we can see many of the cans literally pop into frame when they are being thrown, and pop out of frame when they are close to landing at the other person. Clearly the cans were only drawn into the shot whenever they were being thrown and not whenever they came close to landing or before being thrown. (00:06:26)