Audio problem: When Stifler is driving his car away after he wrecked the flowers, he says, "Fu**ers, it's not my fault," but it's visible through the window that he's not saying anything.
Audio problem: When Stifler is talking to Finch about how he is going to get with Cadence and does the nipple milking impression, during a good portion of the shot that is shooting over Stifler's shoulder to show Finch's face when Stifler is talking, watch Stifler's lips from the side: you can see they are moving out of sync with what we hear, it was obviously changed and dubbed over. (01:12:10)
Audio problem: In the bachelor party scene, when Michelle's dad notices the "mud" (chocolate topping) he says, "We are going to need a mop." Then Michelle's mother says, "I saw it in this closet" except that her mouth does not match up with the audio (it looks like she says "It's in here." (00:51:50)
Audio problem: When the guys are in the gay bar and Stifler says, "I'll show you F***ers," his mouth doesn't move. (00:24:35)
Audio problem: At the gay bar, Stifler says, "What is this, a dance-off?" When he does, you can see that his mouth doesn't move. (00:25:55)
Answer: As I remember, there was a scene where someone says, "Michelle's parents are flying in for the wedding."