Plot hole: The fake Jinx wouldn't be able to get into the den, the door was closed.
Meet the Parents (2000)
1 plot hole
Directed by: Jay Roach
Starring: Robert De Niro, Owen Wilson, Ben Stiller, Blythe Danner, Teri Polo
Revealing mistake: At the airport when Jack says 'tow it', there is an extra waiting for his mark to walk outside seen in the reflection of the doors.
Dina Byrnes: Now Greg, you have a very unique last name. Um, we were curious, how do you pronounce it?
Greg Focker: Oh, just like it's spelled. F-O-C-K-E-R.
Dina Byrnes: F-Focker.
Jack Byrnes: Hmm, Focker. Hmm.
Trivia: Originally, the film was meant to be a vehicle for Jim Carrey. Among his contributions was Greg's surname, "Focker." Eventually, Carrey left the production, and Ben Stiller took the part.
Answer: Greg was probably surprised at just how "richy" they really are. Because lacrosse camp seems like a really rich, preppy thing to do. But mainly, I think he was suprised because he did not know that his girlfriend's ex and his girlfriend's sister's fiance knew each other. He didn't realize how connected they all were.