When Erik and Brandy are in the pool room, when Brandy takes her bra off, Erik hits the cue ball and tosses the pool cue. In the next two shots of Erik the cue ball is in the same spot. Then it's gone again.
At the end of the football match against the midgets, the ball clearly rolls over the line. However, after Rock says "you're still my bitch, Stifler!" the ball is on the pitch again, but nowhere near to Stifler.
When the boys are visiting Stifler in hospital, and he's telling them about the naked mile, he's holding a cup of pudding in one hand and then it swaps to the other end in the next take. This happens a number of times through out the scene.
At the end of the football game the midgets force a fumble with 5 seconds left. They then kick off to the Betas. After a safety, the team who forces the safety receives the following kickoff, the Betas should have kicked off to the midgets.