Revealing mistake: When Louise pulls off Joel's trousers, we see that he is wearing briefs under his boxers.
Revealing mistake: During Stimpson's speech toward the end of the film, you can see that it's John Cleese himself giving his sleeve a good pull under the table, when his taped-on sleeve accidentally comes off.
Revealing mistake: During the earlier graveyard scenes when the zombies or monsters are walking out from their graves, half the makeup is genuine prosthetics, while others are fake thrown together rubber that separates from the actor's faces.
Revealing mistake: During the credits, Don Falcone is reading about the bloody feud between fellow cheesemaking mafia families Lombardi and Zanetti. The first article he browses is the April 7, 1985 edition of the Italian newspaper "Il Messaggero," with a bad glue-on job (the left column's font does not match the rest of the actual newspaper). He then reads about the car bombs in another newspaper, "Paese Sera." Here the prop design is better, but if you can read Italian, you can easily see that the article does not match its headline at all; it's not about a brutal mafia murder, but rather about the "sliding wage scale" referendum which was taking place in the country at the time the movie was shot, in 1985. (00:03:00 - 00:04:15)
Revealing mistake: At the end when Katrina's skeleton flips off Keith, you can plainly see a crew member's hand moving the arm.
Revealing mistake: At the dinner at the Indian restaurant, when Howie Mandel begins eating the flowers, Blake Edwards' daughter breaks character and cracks a smile, regaining the deadpan composure of the role only at the very end and in the next shot. (00:57:25)
Revealing mistake: Vanity's stunt double is obvious as she drives the Corvette under the semi truck's trailer.