[Both sets of parents have walked in on Jim and Natalie having sex.]
Jim's Dad: [to Natalie's Dad.] Hi, I'm Jim's Dad. You must be the parents of this young lady. I didn't get your daughter's name, but I'm pretty sure my son did.
In the scene where the Asian guy is peeing off Stifler's balcony, he knocks over a plant and knocks out Christy. In the next shot the plant is back, and in the one after that it is gone again.
In the scene with Jim super-gluing himself to himself and just after the police tell him to 'freeze', if you listen closely you can hear the radio say 'Right George K' which, if you listen hard enough, is said all the time the police are chasing you on all the Grand Theft Auto games.