Continuity mistake: At the very start, the way the waiter holds the phone changes instantly. (00:01:15)
Continuity mistake: The lettering on the cake at the beginning changes after Stiffler messes it up. It's in a row then diagonal.
Continuity mistake: At the end of the bachelor party, the gay man is talking to Michelle's mum and sits down. He then crosses his legs. The camera cuts and he crosses them again. (00:50:30)
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)
Continuity mistake: During the bachelor party, the cop stripper rips open her top and shoves Michelle's mother's face into her chest. In the next shot the stripper's top is buttoned.
Continuity mistake: When Jim's dad goes to see Michelle (when she's trying to write her vows), her hair and makeup are done for the wedding, and her hair is in a French twist. Later, when Michelle and Jim are having their first dance, her hair is in a curly bun sort of style.
Character mistake: When Cadence meets the group at the airport and Finch comments "you're reading Descartes", she responds by utterly butchering the line "cogito, ergo sum." Odd that a student of Descartes would be unfamiliar with how to pronounce his most famous statement-somewhat analogous to a student of Einstein not knowing e=mc^2.
Answer: As I remember, there was a scene where someone says, "Michelle's parents are flying in for the wedding."