Revealing mistake: When Karen rips open the wrapping on her gift from Harry, in the close-up of the CD as she holds it with her right hand, it is blatantly obvious that it is not Emma Thompson's hand. Just compare it with the earlier shot of her hand when she sneaks a peak at the card signed - "Sorry I'm such a grumpy bugger.. Bad Harry." (01:27:45)
Revealing mistake: Bruce Willis wore fake feet during the movie to protect his own while shooting the film. They were like boots that slipped on over his. At the part where the FBI guy shoots at him from the helicopter and Bruce jumps to a lower level of the roof, you can see the tops of the fake feet that aren't tight around his ankles. (01:50:30)
Continuity mistake: In the scene where Harry and Marv are at the skating rink, the front of Marv's hair is constantly changing from shot to shot. It's either poofy or pulled back due to the earmuffs he's wearing.
Continuity mistake: Bruce Willis is emerging from an underground air-vent when the plane with General Esperanza is landing. Initially the plane is coming on a direct course for him and he struggles to get out. In fact the front wheel is on course with and knocks the vent cover. But in the very next scene, the tire marks clearly show the front wheel passed to the right of the vent and so completely missed it. (01:11:40)
Continuity mistake: When the Griswolds are driving to the tree farm, they are being harassed by the rednecks in the truck. Several shots of the front of the truck show only two passengers, but one view of the truck through its rear window shows three passengers. (00:04:17)
Visible crew/equipment: When a gremlin attacks the Mum from a Christmas tree, and the tree falls on top of her, you can clearly see a member of the crew with eyeglasses, wearing a red shirt, standing behind the tree pushing it forward on top of her. (00:54:30)
Continuity mistake: In the flood scene when Natalie walks in and begins to scream, Kevin is standing on the first step of the stairs with his shirt uneven, and the strings for his pants are showing. In the next shot, Kevins clothes are neatly ironed, his shirt is even, and the strings have disappeared. (00:28:30)
Continuity mistake: When Louie is released from jail his hair is sticking up all wild, then it's flat, then it's all wild again. (00:47:25)
Continuity mistake: In the scene where the girl jumps to her death from the balcony, it shows her hitting the car towards the right halfway onto the windshield. Then in the next shot, it shows her lying right in the middle of the roof of the car. (00:04:05)
Continuity mistake: After Jack is blown out of the sky and is lying in the graveyard, he has several grey smudges on his face from the explosion. But in the very next shot, a bird's eye view of Jack lying across the angel, the smudges have disappeared. (00:59:10)
Continuity mistake: In the scene with Sinbad and Howard in the radio place, Sinbad gets enraged, then throws the package (thought to be a bomb) and Howard hits the deck. The package lands at Howard's head, but in the next shot, it's way over to his left.
Visible crew/equipment: In the opening shot, as the camera moves down the building, in the windows you can clearly see the cameraman & camera on the hoist/crane. (00:01:00)
Other mistake: At the very beginning, when the lights rise above the cast you can see they're all equally spaced out and the light has the same brightness for each character. At the end of the song, the camera shoots to the back filming everyone from behind, note Mark, he's crammed in the corner next to Angel with out the same amount of space originally he started with and his light is very dim compared to the seven others. (00:02:45)