Visible crew/equipment: In the opening scene, the camera and camera man can be seen reflected in the knife.
Continuity mistake: When Bateman goes to Paul's apartment to pack up his stuff to "send him to London" after killing him, as he is packing the bathroom light is off and then about 2 seconds later the light has come on by itself with him nowhere near the room.
Visible crew/equipment: In the office scene when Kimball is talking with Bateman, a microphone boom can be seen in the CD's reflection behind Bateman.
Visible crew/equipment: After the beginning of the movie where there is an aerial shot of New York City just before we see Patrick getting at his office, the filming helicopter can be briefly seen reflected on one of the buildings' glass on the left side of the screen while it films the scene. (00:07:13)
Continuity mistake: When Bryce pulls out Paul Allen's card to show it to Patrick, he holds it in different ways between shots. (00:19:44)
Continuity mistake: At the restaurant, Patrick approaches his lawyer to talk about the answer machine message he left him and the lawyer puts an unlit cigarette between his lips. The cigarette is already lit in the next shot when he mistakes Patrick for another colleague. (01:31:16)
Revealing mistake: When Patrick brings Sabrina into his apartment for a threesome with Christie, as the camera passes the open door to the bathroom, you can see Christie stood still by the door, waiting for her cue to walk in. (00:40:23)
Visible crew/equipment: When Patrick is at the dry cleaners, and arguing with the owners, a woman called Victoria comes in and offers to get Patrick's clothes cleaned for him. Just before Patrick leaves he says "Oh boy, I've got to go. Thank you, Victoria" and you can see the boom microphone reflected in the glass door (just above Victoria's head). (00:14:17)
Visible crew/equipment: The first time Patrick Bateman enters his office (listening to "Walking on sunshine") you can see a boom microphone reflected in the glass partition of his secretary's office area. (00:07:44)
Visible crew/equipment: When Patrick brings Sabrina into his apartment for a threesome with Christie, he says to her "Not quite blonde, are you?" and you can see the shadow of the boom microphone fall across the wall. (00:40:19)
Audio problem: When Patrick Bateman is exercising and watching The Texas Chainsaw Massacre, the audio does not match up with the actual film. (00:37:05)
Visible crew/equipment: When Patrick Bateman is showing Detective Kimball out of his office, the boom microphone can be seen poking into the shot on the other side of Bateman's interior office window. (00:36:46)
Continuity mistake: When Patrick Bateman murders Paul Allen, the collar on his raincoat is either up or down, depending on the shot. (00:27:49)
Revealing mistake: When Patrick opens his fridge to offer Jean some sorbet, you can see the decapitated head of a woman in the fridge. If you pay close attention, you can see the head is moving a little. (00:59:36)
Suggested correction: It's a prop head resting on a freezer shelf. It could simply be that opening the freezer door causes the head to sway a little, similar to if you had an egg, lemon, or something else that didn't have a flat bottom resting on a shelf inside a fridge.
No, the way it was filmed was with the actual actress putting her head up through a hole in shelf. It's her head moving.