Continuity mistake: (DVD only) In the new ending, when Alex attacks Beth at the family's home, Beth has bruises and a cast on her arm, obviously a result of the accident she was in a few days ago. In the original ending, presumably taking place within the same time frame, when the cops come to question Dan about Alex's death, Beth is fine - no bruises, no cast, she doesn't even look tired.
Continuity mistake: When Alex goes to see Dan in his office, Dan in the first scene is sitting with uncrossed legs, then his legs are crossed, then uncrossed again.
Continuity mistake: Early in the movie, there is a black clock on the wall in Dan's kitchen that reads 7:50. Later, when he is in Alex's apartment strangling her, the same black clock is now in her apartment and it, too, reads 7:50.
Continuity mistake: At the end Michael Douglas is standing in front of his home with the door open in the background with the hallway illuminated. The camera angle now switches to inside the house, but he has to enter the house through a closed door.
Continuity mistake: When Dan throws Alex into the bath, she goes in face down, but suddenly she is face up - which would be a difficult manoeuvre in a small bath.
Character mistake: When Dan and Beth are talking on the phone, Beth says Ellen, their daughter, is five years old, but later, when Dan and Alex are together, Dan says Ellen is six years old.
Continuity mistake: When Alex, naked in bed, jumps up to stop Dan leaving, she attacks his shirt, and you can hear it ripping, but, later, it's completely fine - no ripped bits anywhere.
Continuity mistake: When Dan leaves the budget office in his rental car, the front license plate is mounted off to one side, unusual for this type of vehicle. When he arrives at the house, it's still the same license plate number, but the plate is now mounted on the centre of the bumper.
Continuity mistake: When Dan's wife is by the dinner table talking about the house, his arm is up, yet a frame later from a different angle is down.
Continuity mistake: After Alex and Dan go dancing and go back to her apartment, she reaches up to get a door key from the top of an electrical box outside her door. She takes down the key in her right hand and then opens the door with her left hand. The key never goes near the lock or doorknob.
Visible crew/equipment: When Dan reluctantly tells his secretary that he will accept Alex's phone call, if you look in the top left hand corner of the screen, you can see a boom microphone make a quick appearance.
Continuity mistake: Michael Douglas is going home to Mount Kisco the very very long way down Riverside Drive South. Again Alex's tape hasn't skipped a beat.
Other mistake: After Michael Douglas visits his wife in the hospital he drives into New York looking for Glenn Close. During the driving scene he is seen to move the steering wheel to the left, but the car turns right.
Continuity mistake: In the scene where Beth is desperately trying to find Ellen, she approaches a stopped Chevrolet Caprice wagon and rear ends it. When the camera switches to an interior shot of Beth's vehicle during the collision, the vehicle in front has changed to a Ford LTD wagon.
Continuity mistake: While eating together, Alex tells Dan that she stood up her date, and raises her hand. From the opposite angle it's lowered.
Continuity mistake: When Dan and Alex are under the rain, a black man in a gabardine passes by Dan, and a frame later passes by Alex, in the opposite direction.
Continuity mistake: Dan is having a drink with Alex and he talks about his parents' divorce. His glass swaps from being on the table to in his hand between shots.
Revealing mistake: In the first scene where we are introduced to Alex Forrest at the bar during the cocktail party, she is almost always smoking cigarettes that are not lit. She continually dashes out ashes that aren't there and there is never any smoke coming from the cigarettes.
Continuity mistake: When Glenn Close calls Michael Douglas in the middle of the night, his clock radio reads 2:13. In the next shot, without him touching it, the clock is dimmer and has been moved so we can't see the new time. Then about a minute later, the clock radio reads 2:20.
Continuity mistake: Dan throws his umbrella and it bounces on the edge of the wastebasket but lands on the floor. When he walks next to the wastebasket the umbrella is now inside.
Suggested correction: It lands on the ground and stays there.
