Wilma and Johnny put their son to bed in their hotel room and continue their fight. Evidently, they go back down to the reception, leaving the boy in the room, until we see Wilma bump butts with her mother-in-law on the dance floor, taunting Johnny until he flicks her off and she runs after him. However, in the background, both of their sons are chasing each other around and dancing. Did the dark-haired son awaken suddenly and they took him back downstairs?
Near the beginning of the movie, when Gig Young and Cloris Leachman are sitting on the couch with a mirror behind them, you can see a reflection of a crew member in the mirror as he tries to move out of the shot.