Revealing mistake: Just after the scene where the doctor asks Columbo to switch off the light before leaving, the detective does so, but it can be seen that both light switches are down before he does this, and that they are still both in the down position after he "switches off" the light.
Revealing mistake: When we see a vision of Child-Alyssa walking down the street with a sort-of vortext behind her as the cult-members flee, watch closely and the entire shot is comical. All of the extras are barely moving at a jogging-speed despite supposedly running for their lives from her. Several are visible running towards her direction or even directly behind her despite supposedly fleeing from her. Several extras veer off to the side before exiting frame even though there are buildings on either side so there's nowhere to go. And several others still are visible running left-to-right or right-to-left from either side of the frame, again despite there being buildings on either side. Obviously all of the extras were filmed in front of a green-screen being told "just run around a bit" and then added to the scene. The shot makes no sense if you pay attention.
Revealing mistake: When Gretchen gets run over, you can tell that a dummy was used as the car's wheels pass over her. The position of her head changes between shots and her body seems a little too still for a living person who's just been run over. She should have been tossed a few feet or maybe even gotten caught under the car's wheels.
Revealing mistake: When the man is melting after being covered in acid in the beginning, you can see a wire pulling the "melted skin" off his arm, at the bottom of the frame briefly. (00:04:00)
Revealing mistake: As Ted is being burnt by the fire, you can see his body trapped underneath the debris. In a side shot of Ted it is very obviously a stunt dummy as the left arm and head stay completely still and the arm remains completely stiff despite hearing screams and shouts from the pain.
Revealing mistake: When Nick is being followed by the PI, several times Nick's speedometer is seen to be at zero. (00:58:40)
Revealing mistake: When Gabriel Noone goes to see "Peter", he arrives in rural Wisconsin, looks out of the window of his car, and sees a mountain in the distance. There are no mountains in Wisconsin.
Revealing mistake: When the guy that was shot in the chopper is falling, you can see the protective, yet flaming mask on his face.
Revealing mistake: In the very first scene, which takes place in a Moroccan sheepherder's meadow, the camera makes some gentle panning motion. The mountains in the distance can be seen noticeably moving not quite in sync with the foreground. The foreground is actually in Texas (according to the director's commentary), and the mountains were added in post production.
Revealing mistake: When the glove comes up the car seat and into Porter's chest, there are lights from buildings out the side window, so the car isn't moving at all. When it cuts, there's suddenly a hill where the lights should be and now the car is moving again. (00:29:30)
Revealing mistake: The fight scene between Peter Kurten and Andy outside the gay bar is viewed from behind a metal gate. Peter smashes Andy's head into the gate twice. The bars of the metal gate bend towards the camera as if they are made of rubber.
Revealing mistake: When the killer is up in the radio tower, he tries to force the man up the ladder. He brandished a revolver and you can hear the hammer being cocked back. It shows the revolver more and you can see the hammer is still down.
Revealing mistake: In the first morgue scene the body on the table is obviously breathing.
Revealing mistake: As Holmes and Watson are riding home from Watson's stay in prison, in the background double traffic lines are visible as are concrete traffic barriers. These are a modern invention and out of place.
Revealing mistake: A couple cross the road to enter Victoria Coach Station, London. There is the noise of a coach braking hard and they throw themselves away from a coach just inside the entrance, which obviously was not moving at the time. They walk into the station and talk to an inspector, while the same coach is driven out of the entrance past where it is supposedly parked.
Revealing mistake: There are several instances where you can see that the bandages used to wrap up the girls are pre-assembled. When the first girl is "waxed" you can see there are no joins between the bandages, they are all in one piece - almost like a body stocking. You can also see this later with Elizabeth, and it becomes more significant because you see the bandages being wrapped around her head as normal, and then when Watson pulls them off, they come away in one piece like a balaclava, which of course shouldn't happen.
Revealing mistake: When Vanessa comes out of the girls shower and walks to her locker, in the back shot you can quite clearly make out the strapless bra she is wearing under her towel. Also, when she lifts her arm up you can briefly see the black material under the towel.
Revealing mistake: As a homage to the original; when Norman carries Marion's dead body, wrapped in the shower curtain to the car, you can see her bra strap through the curtain.
Revealing mistake: After Lucifer kills Gabriel, we get close-ups of Lucifer where the outline of his contact lenses are visible.
Revealing mistake: When Gittes visits the orange grove and crashes into the tree, you can see that a steel plate has been placed around the tree to protect it.