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 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 Papet peers through a telescope, it's obvious that the lens cap is on.
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: The bulldozer is rusty and covered in mud. When Kong grabs it, it's now a miniature perfectly painted. Also, the driver is an obvious dummy.
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: When Louise pulls off Joel's trousers, we see that he is wearing briefs under his boxers.
Revealing mistake: The chairman parks his car in front of Bel Fuse Ltd. And goes upstairs. His car explodes, but does it in front of a different building, probably switching to a stage building front; the metal doors don't have vents anymore and there are visible join lines in the asphalt and the cement. (00:15:10 - 00:15:40)
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: When the bully's held up by Sam wires can be faintly seen.
Revealing mistake: Vanity's stunt double is obvious as she drives the Corvette under the semi truck's trailer.
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: 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: When Eddy's mother is lying dead on the bed, she is breathing.
Revealing mistake: The scene in the locker room when the bullies are dunking Marty in the toilet. Marty's "body" is a fake prop used - on the naked body mysteriously there is no penis or testicles. In addition to this, despite being turned completely upside down, Marty does not struggle in the slightest as he would in real life - he does not struggle at all exactly because it is a prop body being used.
Revealing mistake: When they're riding with Jones look closely in some shots and you'll see Lea Thompson's stunt double.