Continuity mistake: At the start of the film we are introduced to Michael Douglas' family life. His wife is in the bathroom getting ready for their night out, Michael is sat on the couch reading and his daughter, Ellen, is sat on the chair watching cartoons. In one shot Ellen is sat on her own, but in the next shot their dog has magically appeared on her lap.
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: Dan plays the tape that Alex made in his car. He stops the tape when he gets home, and after he gives his daughter a pet rabbit, he goes to his den and puts the tape in the tape recorder and presses play - that's all; he doesn't rewind it - but what he hears is the same bit he heard in the car, which is wrong; the tape should have started play where it left off in the car.
Continuity mistake: Playland, Rye NY in the spring, summer and autumn. Alex and the girl walking to the Dragon Coaster. It's spring with the leaves in bloom. Then in stock footage of a different roller coaster being pulled to the top, it's fall with the leaves a golden yellow. Then in other stock footage, the trees are a lush summery green. (01:36:35)
Continuity mistake: When Michael Douglas comes home the first night after being a bad boy with Glenn Close, he is shown in the kitchen talking on the phone to his wife at a little after 8:30 AM. Not only does he talk to her, but he also has a whispery chat with his lover, walks all about the kitchen, sits at the table, and the time on the clock doesn't change once. (00:22:20 - 00:23:05)
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.