Continuity mistake: When Lucas visits Meg at the juvenile home, he carries a stuffed toy monkey by the leg. When the camera angle changes, he is holding the monkey by the neck. (01:08:15)
Continuity mistake: At the beginning of the movie (until Wasson's name appears in the credits), James Madison is writing on a paper copying from a large tome. Two people enter the room carrying a trunk. When he stands to go open the trunk and check its contents we can see that the book is gone from the desk. However, we see it again a minute later...when he picks it from those in the trunk and brings it to the desk. The first shot was a repurposed one. (00:00:50)
Continuity mistake: In the beach scene the boys are eating ice cream cones. The ice cream keeps changing size.
Continuity mistake: Sammo Hung just left the bus to ride the bike with his cousin Jenny. They ride talking about Stallone and the USA, and the boxes of Nike shoes are tied to his bike differently when they arrive compared to when they started. (00:23:00)
Revealing mistake: When the Russians are in the Finn's trench, you see the Finns stabbing the Russians. If you look carefully, on a few of the Russians you can see protection visible. (00:48:45)
Continuity mistake: The box of Marlboro cigarettes next to Buster's [Kiefer Sutherland] left hand did not have a lighter on top of it, but there was a lighter atop the pack after an angle shift. Buster was holding a newspaper with his left hand and had a cigarette in his right, so the lighter just suddenly appeared. Seconds later, the lighter was gone. (00:04:34 - 00:05:02)
Other mistake: At the beginning of the film, there's no way Angela would possibly have been able to know the exact moment the girl would have been walking down the street and what she'd be wearing so she could be wearing the exact outfit.
Continuity mistake: John Ritter's beard goes from being real to fake throughout the movie.
Factual error: After the passenger door gets ripped off the Oldsmobile Toronado, a female voice is heard repeating that the "passenger door is ajar." While the Toronado was available with an optional Voice Alert system, the GM system used a male voice.