Revealing mistake: In the opening scene the camera pulls back from a bedside locker to an over the shoulder shot of Kathleen Turner doing her make up in the mirror. Close inspection shows that the shoulder in the foreground is actually that of a double who doesn't quite match Turner's movements.
Revealing mistake: In the scene out West with the buffalo, notice the car driving in the distant background.
Revealing mistake: In the final scene when Annie and Sam are exiting the observation deck coming towards the elevators, the New York skyline backdrop which should be visible behind them is missing, and the entire sound stage wall can be seen beyond the observation deck safety railings instead. 'Although the exterior and lobby of the Empire State Building, 350 Fifth Avenue at 34th Street, are the real thing, a slightly larger replica of the Observation Deck was built in a hangar at Sand Point Naval Base on Puget Sound just northeast of - where else? - Seattle.' https://www.movie-locations.com/movies/s/Sleepless-In-Seattle.php. (01:39:35)
Revealing mistake: During the scene where Ron is playing the jazz flute, as he blows the flame out of the flute, you can see a hose running from out of his sleeve and into the flute, most likely supplying gas for the flame. In both shots of the flame, the hose can be seen.
Revealing mistake: After they kidnap Neil, they are driving to stop the wedding, as they are driving down the road, you can see out the front window that the truck pulls up to a stop light. They cut to Neil and the truck is still moving, then they cut back to the group and they road is clear. Traffic lights don't cycle that fast. (01:20:30)
Revealing mistake: Near the end of the film when Matthew is trying to destroy the pod "greenhouse," there is a shot where Elizabeth walks through. She is supposed to be naked, but if you look close you can see she is wearing flesh colored underwear. (01:55:30)
Revealing mistake: When Sam trips over in the cemetery, she falls onto Dear Johnny's cracked tombstone. As she pushes down, the 'tombstone' squashes under her hands. (00:27:25)
Revealing mistake: When they're driving back to the Darcys' in the snow, you can see that as they pass through the village near the house, the snow on the ground is in fact a white ground sheet and has not been pulled up to the edges of the wall surrounding the green. (01:17:25)
Revealing mistake: After Johnny leaves, they show Baby standing on the porch of her family's cabin. If you look in the background you see two people waiting for their cue before they start walking. (01:24:30)
Revealing mistake: When the truck leaps off the ferry, the underside is seen, exposing the still-flaming 'roll cannon' opening in the rear floorboard. This cannon is what caused the rear of the truck to rise, sending the truck flipping through the air. (01:52:30)
Revealing mistake: In the first scene on Ginger's sister's boat that's being refitted, one of the seagulls (yes they used real seagulls) flies over the stern end right into the cyclorama and takes a nose dive to the stage floor.
Revealing mistake: There is a scene which features a nighttime view of Carfax Abbey, Dracula's home. This movie was set in the late 1800's/early 1900's, but if you look closely at the left-hand portion of the screen, you will see the lights of an airplane as it flies in the skies above the castle.
Revealing mistake: When Cher is robbed and she calls her brother on a payphone, she doesn't put any money in and she doesn't press enough buttons to be using a calling card.
Revealing mistake: The first morning the new Mrs De Winter is at Manderley, she goes to have breakfast, but when she attempts to pour milk into her coffee, there's no milk in the jug; she's just pretending to pour it.
Revealing mistake: Toward the end when Charlotte and Joe are about to make love, it shows him lifting the hem of her black slip. But in the next cut they are kissing again with her slip still on.
Revealing mistake: After Sophie faints at her bachelorette party, during the next scene it cuts back and forth between shots taking place in two rooms - Donna walking into Tanya and Rosie's room, then Sophie walking into Ali and Lisa's room, and both rooms have the very same cracks and stains on the walls revealing it was filmed in the same room, but with different furniture.
Revealing mistake: When Julie is talking to Stuart about her future, snow is falling in front of her. We can also see the wind is blowing, as it moves her hair. The snow, obviously CGI, is still falling straight down, and doesn't interact when the wind blows.
Revealing mistake: Towards the end when Vanilla Ice jumps the motorcycle over Nick's car, you can see the ramp he used through the car's windshield.
Revealing mistake: In the scene where Shelby goes into kidney failure and is passed out on the stairs of her home, Jackson runs over to her and grabs her up. Looking closely, you can see Shelby hold her head up. If she were really unconscious, her head would fall back as Jackson sweeps her up into his arms.
Revealing mistake: When the Japanese planes fly over the hill towards the harbor to bomb it, you can see a cross on the hill. That cross was not there back in 1941 during the raid. It was put there afterwards as a memorial to the point where the enemy planes first came over the hill.