Revealing mistake: As Mary Ann is dying, Kevin is holding her close to him, hugging her. From the behind shot of Mary Ann, you can see, sticking out from behind the right side of her neck/hair, is a tube and the yellow packet that held the blood/pump. (01:53:00)
Revealing mistake: Just as the bus begins to roll down the mountainside, cables are visible which were holding the bus in place. Most easily seen during the first complete rollover. (00:05:45)
Revealing mistake: When the detectives were listening to the message on the answering machine, we heard it say the date was Thursday and states a time the message was left. When the camera shows the answering machine, you can see the display blinking between 1 (the current message) and CL (which indicates the time and date have not yet been set).
Revealing mistake: When David is sitting in L.E. at the end and the camera is zooming in on his face his mask changes. In the very last shot of him just about to pull it off it's much wider/looser so it'll come off easier.
Revealing mistake: In the scene where Murdoch falls off the building, you can see the rope that is holding him up, twice. (00:59:00)
Revealing mistake: In several scenes of the zombies swimming under water, they are obviously holding their breath. Would a dead zombie need to do that?
Revealing mistake: When the bats invade Dr. Dunwoody's bedroom, you can see the strings on one of them.
Revealing mistake: Near the end, when the captain is walking out of the labyrinth holding the baby, you can tell it's a dummy. The baby does not move in the slightest, you can't even see it breathe.
Revealing mistake: Just before Charlie is stabbed you can see the "blood pack" under his shirt.
Revealing mistake: When Chelsea is on the roof of the house and Kathy joins her, Kathy's hair is blowing in the wind, while Chelsea's stays perfectly still, the water in the lake is also perfectly still. Obviously the director had the actors do the scenes separately until we see them both together in which case both characters hair is blowing around. (01:27:40 - 02:00:00)
Revealing mistake: Near the end the psycho killer pays a black man to beat him up so that he can then blame the injuries on Dirty Harry. Watch the killer's hairdo as he gets punched and beaten: a couple of rear-view scenes show an obviously fake wig, intended to look like the killer's own bad-hair-day style. (01:16:05)
Revealing mistake: When Clint Eastwood and detective Jay Winston are talking in her office she walks over to the blinds and touches the plastic piece that closes them but nothing happens, they stay the way they were. She does this twice. (00:25:46)
Revealing mistake: The fire engine often shows up on the scene without any hose in the hosebed (on back of the truck).
Revealing mistake: When MacReady burns the one "Thing" with the split head, in one shot it walks by MacReady in the foreground, and you can tell in that shot that it is just a still dummy burning, as it isn't moving at all. It just sort of floats past with its arms at its sides, while in the previous and next shots it is wildly moving around, arms flailing.
Revealing mistake: When Robert Downey Jr. is taking Halle Berry's blood pressure, the needle doesn't move as he pumps the hand inflator.
Revealing mistake: When the killer is dragging the girl's body with the meat hook, you can easily see that it is a doll. (01:18:45)
Revealing mistake: In the scene where Tom Cruise is yelling at/questioning Dawson at the jail in the witness room, immediately after Cruise gets up in Dawson's face and says, "I'm the only friend you've got," Cruise is supposed to simply turn and walk away. But you can see from the angle behind Dawson that Cruise' first step is a step down, indicating that he was on a pedestal of some sort to bring their heights closer together.
Revealing mistake: The roller coaster used for the Devil's Flight is really the Corkscrew at Playland in Vancouver, where all three movies were filmed. If you look during the opening credits, you can see the name "Corkscrew" up in the lights above the coaster. After this, it says Devil's Flight during the rest of the roller coaster scenes.
Revealing mistake: When Sandra Bullock and Nicole Kidman drag her sister's "dead" husband/fiancé into a room, the door hits him on the head and his eyes move.
Revealing mistake: On each of Sky Captain's hangar doors, the windows are broken in the exact same places, indicating the same window rendering was simply duplicated to make the others. (00:16:45)