Continuity mistake: Pay attention to the items behind the police auctioneer. In the first couple of shots we see a statue of a knight on a horse to the left of the auctioneer. When the camera cuts to Peter, and then cuts back, the statue is gone. The statue is then back in the next shot.
Continuity mistake: In the scene when Peter and Brian crash through the wall in the car during dinner, Lois is standing by the table with oven mitts on. In the next shot when Lois asks Peter what he's doing the oven mitts are gone. There was no time to take them off and nowhere to put them either.