Revealing mistake: In the hut in the swamps Zack lights a candle. The resulting light is obviously from a spotlight because the flame and the shadows are perfectly still. (01:09:30)
Revealing mistake: When Sean Connery and the others are examining the corpse found in the water, the dead body's eyes blink. (01:01:05)
Revealing mistake: When Papet peers through a telescope, it's obvious that the lens cap is on.
Revealing mistake: When Danny DeVito brings home the 'bigger dog' he says for the new dog to go eat the little dog that always bothers him. He lets the dog go and the dog goes after the little one. But when they show the dog chasing the little one he almost runs right past him. There must have been a trainer on the other side of the set calling the dogs to come over because he wasn't chasing the little dog. (00:40:30)
Revealing mistake: When Arnold throws the bad guy through the glass door at the dress shop, it shatters a split second prior to him going through it. (00:55:40)
Revealing mistake: At the end of the movie, the main creature has the head of a human. However, in a number of shots you can see the actor's neck showing how they made the head "appear" to be attached to this creature.
Revealing mistake: The laser blasts the robots fire instantly exterminate or destroy most everything in their path. However, when the guys are shooting at them during the mall blast-out, the lasers suddenly don't do much damage at all.
Revealing mistake: As Sgt. Highway turns the dead body with a cigar in the pocket you can see its right arm move to avoid twisting. (01:38:05)
Revealing mistake: When Howard's running from the female bikers, Satan's Sluts, look closely at one and you can tell it's a guy in drag, one wearing a dark blond wig. (00:10:00)
Suggested correction: I was in this part of the movie, everyone in this scene (except for the duck) is female.
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: Binky and Turnip are waiting for Ted Danson to show up at the racetrack to place his bet. Turnip starts the first sequence peeping from holes carved into the magazine. As he begins walking, notice an old man with a grey jacket and a blue shirt, reading a newspaper, sitting, and immediately after he comes in frame, an elderly couple coming in from the left. The man is wearing a brown suit and shirt about the same colour. When there's the first cut (after the odd guy sticks the tongue out), the two are rushing towards the entrance, opposite way from before, and there's the blue shirted old man standing, and a moment later there's the brown shirt guy passing by, just fresh off walking in and with another person, not the woman from before. The same guy is also seen in the bathroom in the next scene. (00:18:20 - 00:20:10)
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 Norman drives Dukes car into the pond, it's obvious no one is in it.
Revealing mistake: Von Ragnar's body is obviously a dummy as it falls off the dam and onto the rocks below.
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: When the bully's held up by Sam wires can be faintly seen.
Revealing mistake: As the bad guys' Ford pickup flips end over end, the device making it flip is briefly visible. Also, the "bad guys" still in the truck turn out to be dummies.
Revealing mistake: Obvious stunt man for Carrie Snodgrass due to having brown hair while she's a dark blonde when hanging from an axe handle near the end of the movie. (01:35:09)
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.