Revealing mistake: When Karen rips open the wrapping on her gift from Harry, in the close-up of the CD as she holds it with her right hand, it is blatantly obvious that it is not Emma Thompson's hand. Just compare it with the earlier shot of her hand when she sneaks a peak at the card signed - "Sorry I'm such a grumpy bugger.. Bad Harry." (01:27:45)
Continuity mistake: During their sightseeing in Italy, Sarah and Tom pose for an artist who sketches the two of them. In the first shot, their portrait is tacked on the left of the easel with two other portraits. In the next close-up, their portrait is tacked on the right of the easel. (00:55:30)
Continuity mistake: When John says, "You offend reason sir," Peter floats up. The large light fixture is hanging from the ceiling. However, in the next shot facing Peter when he says, "Just think happy thoughts," where is the light fixture? It's gone so Peter can fly around the ceiling, but it's back again in later shots. (00:21:15)
Continuity mistake: NBA Finals-Game 1. Andie wants Ben to buy her a Coke. During this scene, the camera cuts back and forth between Andie and Ben, and the basketball game. When Ben first looks at the game clock there is a little over a minute left in the game. He rushes to get her soda, and when he gets back, she says she wanted Diet Coke. There is a shot in this sequence where the camera is filming the basketball action, and you can see the game clock with over 7 minutes remaining, even though they are supposed to be nearing the 30 second mark. (00:33:35)
Continuity mistake: After their encounter with the monks, Buddy and Dave speed off and come out onto a road. The first shot sees the whole car come onto the road, where there is a double unbroken line in the middle of it. The shot changes to Buddy and Dave in the car. Watch through the back windshield. The double unbroken line has turned into a single, broken line. (01:07:35)
Continuity mistake: When Stifler has the "truffle" in his mouth, there is none over his teeth. Then there is loads all over his teeth instantly. (01:07:15)
Continuity mistake: When Bob puts Charlotte into her bed, he first lays her down with her skirt slightly pulled down so that her belly button is showing. In the next shot, the skirt is pulled up to meet the bottom of her shirt-barely any skin is visible. (00:52:15)
Continuity mistake: After Signor Martini tries to find the snake in Frances' house he lights the stove with a match. He then places the match box on top of the stove with the long side of the box facing the camera. In the next several shots the box turns to the narrow side facing front and then back again. (00:45:20 - 00:47:00)