Revealing mistake: When Hans discovers the first bad guy lying dead in the lift ("Now I have a gun - HO HO HO!") and pushes his head, the corpse is moving his head before he is hit (watch carefully). He also closes his eyes before Hans makes contact. (00:39:15)
Revealing mistake: In the final scene as Doc tell Billy good-bye if you look up to the top right hand corner of the screen you can clearly see a jet trail in the blue sky. Certainly not possible in those days. (01:42:20)
Revealing mistake: Any time when the two girls are in hell's corridors and running around, you see these corridors as stone walls, yet whenever they back up against one of these walls, you can clearly see they are merely rubber sheeting overlayed on a framework as the rubber sheeting bends and contracts very clearly.
Revealing mistake: Near the end of the film, a B-52 seen flying across the screen. The bracket holding up the model is visible.
Revealing mistake: When Les' mom is doing the laundry and "finds" the Test Failed notice, you can see that she actually had it in her hands the entire time. She transfers it from one hand into the other, then puts the hand with the paper into the pocket and pulls it right back out, then knocks it off onto the floor, and acts surprised.Macalou
Revealing mistake: Apparently filmed inside an old warehouse, heavy masonry walls can be observed during some scenes inside what is supposed to be a spaceship.
Revealing mistake: We know that the blob dissolves flesh and hair and that it can also burn wood (since fluid coming from the blob burns a small spot on the desk in the hospital) and that it can dissolve bullets, but despite this obvious acidic state, the blob doesn't dissolve plants, walls, glass, concrete, metal, nor sticks and twigs.
Revealing mistake: When Carol Anne has been hypnotized by the shrink, a hand breaks through the desk and throws a coffee mug through the mirror. You can briefly see the reflection of the plexi-glass protecting the actors behind the mirror as the mirror breaks.
Revealing mistake: After the shootout in the hotel, the police photograph the bodies of the dead cleanheads. The flash of the camera causes the "dead" men's eyes to blink slightly.
Revealing mistake: The dead cop can be clearly seen sitting up even though he's dead as the lady cop tosses the chair through a window. The next shot he's back to being dead again. (01:16:00 - 01:17:15)
Revealing mistake: Near the end, Dundee captures Rico (the bad guy) and changes clothes with him. Dundee is at least 6 inches taller than Rico, yet the traded clothes fit both men perfectly.
Revealing mistake: In the upstairs bedroom scene after the police and FBI serve the warrant at Niko's home. Sharon Stone is there with the baby. There is a shouting match between Niko and another officer. The Officer yells "take it easy, Steve " or "take it easy, Steven". His line should have been "take it easy, Niko"Mike Shaw