Continuity mistake: When Pinhead raises his blade to kill Joey, it's in his left hand. Suddenly, he's transported to the room with Elliot Spencer, and it's in his right hand in the next shot.
Revealing mistake: When Joey stumbles into the church, there are a few wide shots where you can tell the background is mostly a matte painting. What gives it away is that the candles in the foreground are flickering while the candles in the background aren't since they're painted.
Continuity mistake: When Joey drives up to The Boiler Room to find Doc, it alternates between not raining and downpouring, depending on the shot. (Ex. In the shots inside the car looking out, it's not raining. In the exterior shots of the car, it is.)
Audio problem: When Joey calls Doc and he asks her what channel she's watching, she says, "Uhh 12, I think." Her lip movements don't quite match the dialogue.
Continuity mistake: When Pinhead appears in the nightclub, there's a dramatic shot revealing him, and if you look, there's only one or two people to the left of the stairs. The scene then cuts away for about a second and a half, and when it cuts back, suddenly there's a whole crowd to the left of the stairs. Far too many to appear in such a short period of time.
Audio problem: During Joey's dream, as Elliot Spencer says, "Would you walk with me?" and they walk away from the camera as he begins explaining what's going on, their mouths aren't moving at all, and yet there's dialogue throughout the shot.
Continuity mistake: When Joey has the dream where she finds the radio in her closet, there are a few quick close-ups of her hand turning the radio dial. These close-ups are done with a hand double because you can see that the hand turning the dial has a clubbed thumb (sometimes known as a "short thumb" or "toe thumb"), whereas in other shots, she has a normal thumb.
Other mistake: After JP gets the pistons shoved through his head, there's an incredibly puzzling insert shot where we see him crumple to the floor. Suddenly, there's smoke coming off his head, his pants are different, his belt has disappeared, and the pistons on his head are randomly much shorter. It's almost like a snippet of an unfinished effects shot was randomly inserted into the scene.
Revealing mistake: When JP gets the two pistons shoved through his head and we see them "break through" his head, you can tell it's just two different takes of the same effect, since both come out ABOVE his ear, whereas when we see the final result, there's one coming out BELOW his ear. (The hairline on the fake prop head is also a little wonky.)
Continuity mistake: When Terri goes back to JP, when he's talking about "getting this out of the way", Terri's hands go from down by her sides to nervously up by her mouth between cuts. Yes, her back is to the camera in the first shot, but you'd absolutely see her arms move, and they don't.
Continuity mistake: When Terri goes back to JP and they're talking about the girl who "helped" him with the Pillar, when JP says, "You know what I mean, right?", Terri goes from facing him to facing away between cuts.
Deliberate mistake: When Joey is watching the tape of Kirsty Cotton, right as the scene ends, the TV screen cuts to static. However, when we see the final shot of Joey, we can see the TV screen reflected in her glasses, and it's not showing static, but rather a picture of Elliot Spencer. It seems to be a shot taken from earlier in the scene that they laid in at the end.
Revealing mistake: When Pinhead is in the statue talking to JP, you can see where the makeup ends around his mouth/lips during his close-ups, especially when he spits out the bullets.
Continuity mistake: Right after Sandy's skin is ripped off, there's a shot of the camera moving towards her face as she screams. (Right before Pinhead yells.) When this happens, you can see the chain around her left shoulder fall off right before the shot cuts. It's back on her shoulder in the next shot. It happens quickly, but it's super noticeable if you pay attention.
Continuity mistake: When the statue comes alive and kills Sandy, as she's lifted from the ground, the statue's mouth is suddenly open, but it's closed in the shots before and the shot after.
Continuity mistake: When JP sits down next to Sandy and says, "Welcome!", his cigarette goes from in to out of his mouth between cuts.
Audio problem: When the passerby is telling Joey and Terri that the gallery has been closed, he pulls his little dog away, and it makes a horrible yelping and then growling sound. But the dog isn't making those noises, and they're just overdubbed to add a laugh to the scene.
Continuity mistake: When Joey and Terri arrive at the Pyramid Gallery, after the knock, Terri's hand goes from her side to pressed against the door between cuts. Her cigarette also goes from her mouth to in her right hand in the same cut.
Other mistake: When Terri is cooking breakfast and burning everything, there are multiple shots showing a ludicrous amount of smoke coming out of the toaster, implying she's burnt the toast inside. When Joey pulls the bread out, she pulls out two almost perfect looking pieces of toast - brown with just a tiny tinge of burn around them. Certainly nothing that could cause smoke to pour out of the toaster. (Joey also reacts as though the toast burns her fingers, so it wouldn't be crumbs burning up.)
Continuity mistake: When JP gets his hand bitten by the rat, after he throws it away from him, there's a close-up of his hand covered in blood. In every shot before and after, there's little to no visible blood on his hand.
Chosen answer: It's a piston. 2 piston rods are jammed through his head and they move powered by something unknown. You can see the crank shaft and part of some sort of cylinder. A piston is part of an internal combustion engine. It's part of his cenobite form since he liked cars.
lionhead