Continuity mistake: In the scene where Stifler is kidnapped by the little people, the outside passenger mirror on the van changes between shots. Viewed in the shots outside the van, the mirror is in it's normal location. From shots inside the van, looking out, the mirror is pushed forward, making it impossible for the driver to see out of that mirror.
Continuity mistake: In the hospital scene the pudding cup in Stifler's hand keeps jumping from hand to hand whenever they go from close up to wide angle shot.
Visible crew/equipment: When Cooze is stuffing ice down the back of his jeans at the end of the party, his mic wire is visible.