Revealing mistake: When Bernard throws his gun to the ground, the ground "wiggles". (01:09:15)
Revealing mistake: Toward the end film when the female counselor finds Uncle John dead and a camper hanging, the hanging camper's eyes are shaking as he's trying to keep them open in a certain way.
Revealing mistake: In the scene where Zuckerman is thrown to the floor in the gym and handcuffed, you can hear the handcuff ratchet click as it's placed and closed on her wrist. As the other agent moves away, you can see that the handcuff is open and not actually closed around her wrist. (00:31:00 - 00:31:50)
Revealing mistake: When one character's killed, stomach sliced open, you can see the wire yanking open the prop stomach to the left of the camera.
Revealing mistake: The palm trees next to the building Arthur came out were not real trees. One is flush against the front wall of the building and another is in a nearby corner. The palm tree in front looked completely flat - like a large piece of cardboard or maybe painted on the wall. Palm trees should be at least 30' away from a structure as well as outdoor pipes, buried lines, etc. They grow a big central root below the trunk and MANY thin roots running horizontal close to the surface - some may be exposed. (00:05:51)
Revealing mistake: When Dolph goes into the bar near the beginning, he headbutts a bald guy. You can see that he doesn't even come close to making contact. Still, the guy has a broken nose.
Revealing mistake: Clearly not Susan Blakely when she goes topless. Her hair suddenly becomes curlier, that's a body double.
Revealing mistake: When Jemma enters the headshrinker's laboratory, there is a table with three heads on it each encased in glass. When it goes in close-up on the middle head, you can see that the table has a hole where the actor can slip in his head.