When Jim "glued himself" and he cannot get any help, then he goes to the roof, he seems to have been able to put on boxers, shorts and shoes. How was he able to do that, but he was not able to open a door or call someone?
When Sherman and Jessica are talking on the front porch and she calls him out on his "Terminator" references, she remarks about how "The Terminator" was a hit movie "like 10 years ago." In actuality, "The Terminator" was released in 1984 - 17 years prior to the release of this film (in 2001).
When the girls parents walk in the dorm at the beginning of the movie, they both call her by her name, Natalie. Right after, Jim's dad says he didn't get her name but both her parents had just said her name was Natalie just seconds before.
When Stifler throws the football at the girls on the beach and Oz dives into them, the 2 liter of Pepsi is half full and upright. Before he falls, the bottle is crushed and to his side. He never touches it.
At Stifler's party, when the Jim, Finch, Kevin, and Oz are sitting at the table, they are playing cards. There is a pile of cards in the middle of the table, but when the cops come inside to bust up the party, the camera flashes back to the table and the cards are gone.
During the scene with the 'Lesbians', Amber pulls down her bra to her waist. A few shots later, she pulls her bra back up again. In the very next shot her bra is round her waist again, and in the next shot it's on her chest again.
When Kevin is telling the guys about him and Vickie, whilst sat on the rocks near the end of the film. The wide and close up shots of all characters besides Kevin show there backs to the water, but then the close up shot of Kevin shows the sea behind him.
When Stifler comes in the room with a box of pornographic films, he throws one film at Jim and the film is shown falling early by his legs making him stretch for it. The next shot it hits him perfectly in his arms.
When the guys enter the town for the first time, in the shop window reflections, you can clearly see in some shots that the pick up truck is strapped to a trailer and being towed, as well as having a camera crew on it.
The guys are using GMRS radios during the lesbian scene and they're talking to a trucker, and the little boy and the fast food joint. Truckers don't use GMRS they use CB's. It would be like trying to tune an AM radio to 88-107.9FM and getting a FM radio broadcast. Completely absurd. Similar mistakes were made in The Blues Brothers & Die Hard.
In the beginning scene in which Jim attempts to have sex with the girl, it is established that they are in Jim's dorm, allowing Jim's dad to walk in on them. How did the girl's parents know where to find her?
At about the 28 minute mark "Michelle", played by Alyson Hannigan, is teaching a group of young flutists. When they bell rings and they start to walk away you can hear one of the girls say "Bye, Alyson" instead of using her characters name, "Michelle".