9. The Magically Appearing Ambulance - Die Hard
Die Hard is a virtually perfect movie - a fine-tuned, ludicrously entertaining exercise in suspense, and one with generally water-tight internal logic.
Except, where the hell did that ambulance come from at the end of the movie?
As Hans Gruber (Alan Rickman) prepares his escape from the Nakatomi Plaza, we see tech support Theo (Clarence Gilyard) driving an ambulance out of the giant truck the terrorists themselves emerged out of at the start of the movie.
But when the terrorists all walked out of it, the perspective made it abundantly clear there wasn't enough room to contain all these men and an ambulance. So, uh, what's the story?
Director John McTiernan has copped to the mistake, admitting that it was simply due to the film's script being changed during production, and so he had no idea the ambulance would be coming out of the truck when he shot the terrorists' entrance.
But considering that the mistake only became widely known in recent years after co-writer Steven E. de Souza explained the reasoning behind it, it's safe to say that 99.8% of people who've ever seen Die Hard wouldn't even think about the ambulance.