House on Haunted Hill (1999) - 5 major mistakes

Deliberate "mistake": When Eddie and "Jennifer" are walking around the house alone, "Jennifer" is trying to tell Eddie that she's really Sara. But By the time she is explaining that her name is actually Sara and not "Jennifer", Eddie has disappeared. She doesn't find him until later... But from the moment she finds him (and he is talking to her) he calls her Sara... but he never actually heard her say that. He was gone. Also, after they all get back together, a few of the other people start calling her Sara as well....but no one actually heard her say that her name was Sara.

Revealing: When the house has been locked down at the beginning of the film no moonlight could come in, however when the guests are being shown the coffin with the guns in there is a shaft of bright moonlight shining on to it.

Revealing: In the scene where the girl is going to shoot Vincent Price watch closely as she pulls the trigger. You can see the wires pulling the gun from beneath to give it the realism of the blast.

Continuity: Right after Evelyn gets electroshocked, Blackburn takes off her mouth guard and a pool of blood leaks around her lips and down the side of her cheeks. In the next shot, there is a little bit on her lips, and a lot down the side of her cheeks, and several shots later she is seen with only a little dribble down her cheeks and none on her lips.

Factual error: In the scene where the cast find the guns in the tiny coffins, they mention that it is not possible to tell if they are loaded because the clips are welded. Being semi-automatic pistols, simply pulling back the slide & ejecting the first round would have easily determined whether live or blank rounds had been loaded.