Revealing mistake: In the early part of the film, Beverly D'Angelo and Chevy Chase check into the hotel/motel. She goes in to take a shower but he barges in. If you look real closely, she is wearing underpants and is not nude although she is taking a shower.
Revealing mistake: In the scene on Christmas morning when the Bumpus' dogs run in and eat the turkey, during the shot of the dad sitting in the chair reading the comics, one of the dogs bumps the camera and jostles it a little bit.
Revealing mistake: After the baby eats the chili, Jack comes out of her room holding a clean diaper with tongs and puts it in the garbage bag. It should have been a dirty one.
Revealing mistake: At the beginning of the film, Bond is on a training exercise to free a trapped hostage. Since it is only a training exercise, everyone involved is using blanks in their weapons. Why is it that when Bond fires an automatic rifle, we hear multiple bullets ricocheting? (00:03:25)
Revealing mistake: Just after Mr. Creosote explodes and all of the guests are vomiting, there is one male guest third from the front that is puking. Though his hand is up near his mouth, it is clear that the puke actually comes from his hand rather than his mouth, revealing that he is holding something that produces the fake vomit.
Revealing mistake: When Superman gets blown away by the bombs, he is being smashed onto the rocks. You can easily see that the rocks aren't real, but also that when he rises up again, you can see the cardboard rocks dent.
Revealing mistake: When Joel rides his bicycle to the train station, the film is reversed. The numbers on the train that goes by are backwards.
Revealing mistake: When Aurora sees Breedlove off at the airport they say good-bye and he walks through the door, which closes after him. After a few seconds she comes back to talk to him once more, and you can see through the tinted glass panes that he had been waiting right behind the door to come out again. (01:44:20)
Revealing mistake: The little sister says she didn't mean to back into the record player, but just before, she very noticeably makes an obvious move toward the record player. (00:53:30)
Revealing mistake: When the cat rips the painting, it is already damaged before it touches it.
Revealing mistake: This sequel is supposed to take place around 1955 or 56. However, Ballbreaker sports a very 1980s long jumper sweater and leg warmers (popular fashion trend during the 80s) throughout much of the film. Instead of the traditional era coach's jumpsuit worn in Porky's.
Revealing mistake: When Doctor Detroit and his girls make their escape from the automobile salvage yard, they drive a wrecker straight through a large sliding wooden gate, which punches a perfectly clean outline of the truck and Doctor Detroit through the gate. Problem is, the resulting (pre-cut) hole does not match the dimensions of the wrecker or Doctor Detroit at all. In fact, at the point of impact, the stuntman playing Doctor Detroit hugs in close to the wrecker for protection as it plows through the gate, and the outline of his body just magically opens up two feet away from him.