Continuity mistake: In the beginning of the film, when De Niro is holding the cat explaining to Pam and Greg how he taught the cat to use the bathroom, the cat changes from shot to shot. In some shots it's a very fluffy Himalayan with a lot of black on its head, then the next shot it's a much less fluffy cat with more gray on its head. The positioning of the cat in De Niro's arms also changes from shot to shot in this scene.
Continuity mistake: During the scene when everyone is gathered around discussing the whereabouts of Mr. Jinx, Jack announces "We'll just have to reschedule..." Debbie jumps up from the couch and when she does she hits the coffee table causing one of the edges of the table to fall and hit Denny's knee. The next shot the edge is back in place off Denny's knee and Denny has slightly changed positions.
Continuity mistake: Before and throughout the scene where Jack demonstrates his hidden cameras, the lemon and cherry in Greg's glass keep moving around.
Continuity mistake: When Greg is trying to open the suitcase, the top pouch is empty, when the delivery man drops it off, and when Jack tries to open it, the top pouch is full.
Continuity mistake: When Pam is ringing Greg near the end, Jack is watching from the side, and it is obvious how much longer his hair is compared to the rest of the movie. His hair is quite short in the rest of the movie. So it is obvious (since he looks younger in that scene) that that scene had been shot near the start of the filming.
Continuity mistake: For the first half of the movie, the cat's tail changes colour from black to light brown, to black again.
Continuity mistake: When Greg is at the airport's lost luggage department you see the baby chuck up on him but you can see it actually comes from too low down. (00:08:00)
Continuity mistake: At the dinner table when Greg is trying to open the champagne, Pam look straight ahead startled for a second, then in the next frame she is talking to her dad again. It looks like she is seeing the urn hit before it is in the film.