Revealing mistake: In the Director's Cut ending when Audrey II eats Seymour, it spits out his glasses, and they land in front of the camera. They pulled this off by having a pair of glasses inside the plant's mouth that would be yanked out by a string, and another pair of glasses would be dropped in front of the camera. However, the first pair gets caught in the teeth and fall back inside the mouth, but the other pair lands on the ground anyway.
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: The money delivery went awry, and Rambo is fighting the bad guys. He subdues one in armlock, but another charges at him using a lead pipe like a spear. It is rather obvious that the weapon is miles away from connecting to David Chiang's face, but the sound played is one of a hit, and he acts like that. (00:31:30)
Revealing mistake: When Louise pulls off Joel's trousers, we see that he is wearing briefs under his boxers.
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: In the taxi scene Ferris' dad is reading a newspaper. On the front page is an article with the headline "Community rallies around sick youth." As the camera zooms in it's a fake headline to a real news article. The news article begins, "A Chicago policeman killed himself today after he... a Park Ridge office and... workers with a... revolver as he searched for his estranged wife who was hidden beneath a desk by a fellow worker".
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: At the end when Katrina's skeleton flips off Keith, you can plainly see a crew member's hand moving the arm.
Revealing mistake: When the crocodile attacks Sue from the water, it holds on to her canteen for two shots. You can see that the animal actually holds on to a prepared version of the canteen - it is cut in half, with its lower teeth inside to hold it more "comfortably" during the pull.
Revealing mistake: Vanity's stunt double is obvious as she drives the Corvette under the semi truck's trailer.