Continuity mistake: After Barry has jumped into the water reclaim the crown, he comes out of the water with a perfectly clean shirt, but in the next shot the blood is back on his shirt as expected. (00:22:50)
Continuity mistake: As Brian lands the plane down to Bangor, his headset is on in a frontal shot, but in a reverse shot it isn't. (00:47:05)
Continuity mistake: The Bird of Prey is the one captured by Kirk's crew in ST III. That ship's bridge showed Klingon Cmdr Kruge in his elevated command chair with his helmsmen arrayed circularly below him, and nothing else. ST IV has this same ship; however, the bridge now resembles The Enterprise layout with Kirk's command chair behind Sulu and Chekov at their rectangular helm, with Spock, Scotty, and Uhura at their usual positions.
Suggested correction: According to the captain's log at the beginning, they have been on Vulcan for 3 months. As they prepare to depart, we see several Vulcan technicians moving equipment in and around the ship. It's quite conceivable that the bridge was reconfigured according to the crew's specifications to facilitate their use of the ship. This may seem a bit excessive, as the remodel includes the door onto the bridge, and the frame of the door, and possibly most of the rest of the ship. But it's not outside the realm of possibility. The real mistake, though, is why they would go to the effort of installing new workstations on the Klingon bridge and marking them with Klingon labels, instead of standard Federation text. Interestingly, though, the "Starfleet" style bridge layout of the Klingon ship is being used by the Klingons on the Bird of Prey in Star Trek V.
Continuity mistake: Eddie drives a 1957 Chevy convertible off the bridge. A scene showing the car being fished out of the water clearly has an older vehicle dangling from the line.
Suggested correction: The car pulled onto the bridge is absolutely a 1957 Chevrolet convertible.
Continuity mistake: Samara, as seen in the psychiatric sessions on the videotape, has a prominent gap in her front teeth - yet when she decomposes in Rachel's arms down in the well, the skull that is left has perfect teeth with no visible gap.
Continuity mistake: Nick's character is eating an ice cream in the police car and eats the whole thing. When the shot changes to Simon's side, he's still got about half of it left.
Continuity mistake: In the opening scene, Mort closes the door of his jeep before he goes into the hotel room. You can hear the sound of the door closing and it's visible in the rearview-mirror. As the camera moves out of the room, the jeep door is completely open. (00:02:05)
Suggested correction: The door just didn't actually catch. I've had cars like that, especially during the winter.
Given that we see it stay closed for almost 4 seconds and hear it catch, it's a valid mistake.
If you've ever lived where it snows a lot, you'd know that door catches accumulate moisture (ice) and can open slowly, as it did in this case.
Continuity mistake: In the Moscow car chase, Bourne's car is hit from the driver's side by a patrol car. The driver's side window breaks. In the next few shots, you do not see any broken glass on Bourne. In the very next shot the car is not damaged on the driver's side. (01:25:25)
Continuity mistake: When Bourne is talking to Firsch, the gun he is holding changes from a Glock in the shots facing Bourne, to a SigPro when the shots face Firsch.
Continuity mistake: In the scene where the police car is chasing Ben Affleck and Uma Thurman on a bike down in a tunnel, in one shot, the police car's flashing light on top is ripped off by the low ceiling. In the very next shot, the lights are still on the top. The next shot shows the lights are gone. (01:13:50)
Continuity mistake: When Frank Walker and Casey Newton get into Frank's bath to escape the robots, Frank gets in on the left and Casey gets in on the right. They get shot off but when they land in the swamp, Frank is on the right and Casey is on the left.
Continuity mistake: In Nancy's final showdown dream, she goes down to the cellar, then goes to open the door which leads to the boiler room. When she opens the door it's hinged on her right hand side, yet when the shot changes the door is now hinged on her left hand side. (01:13:25)
Continuity mistake: When Dr. Gordon picks up his tape, the way he holds it changes instantly. (00:06:50)
Continuity mistake: When Suzie pours champagne on Kelly's chest,from shot to shot she sometimes has champagne on her chest and sometimes doesn't.
Continuity mistake: When Frankie is about to receive the first stigmata (when sitting in the bath), a pigeon suddenly flies up. When she takes a piece of a feather that flew into the water, you can already see stigmata marks on her right-hand wrists.
Continuity mistake: In the scene where Eddie Murphy is going into the crypt, he takes one of the lit torches. While they are trying to escape the skeletons, the door to the crypt closes and locks. When they show the shot of his son outside, you see two torches again. When he gets the doors open and they leave, you see one.
Continuity mistake: When they are all outside and MacReady has separated the three most likely suspects and orders that they be tied down and tested, he comments at that time that they are to be hit by a storm in six hours. Cut to the scene where Mac is dictating into his recorder and he comments that the storm has been hitting them hard for 48 hours. However it is the same night and at best, maybe only an hour has passed.
Continuity mistake: There is a scene in which a ghost shoots harpoons through the back door of the Mystery Machine. In the next shot, the harpoons are gone, and when the van gets back into the city you see a shot of the back and there is no damage whatsoever. (01:03:20)
Continuity mistake: In the scene where Thora Birch's character goes to a café with her psychologist, the psychologist takes a bite of a cake and puts it back on the table. In the next scene, the cake has not been touched.
Continuity mistake: At the end of the movie when the mob guys come to the boat house to move the body, Barry the Blade shoots a raccoon with his gun which has a silencer. But, later when Reggie shoots the neighbor's alarm system with Barry's gun, it does not sound like it has a silencer anymore.
Suggested correction: The silencer fell off the gun when "the blade" tackled the kid and Reggie. They show the silencer falling off the gun into the leaves.