Yippie-ki-yay, Mr. Falcon.
Willis' hearing was injured: Director John McTiernan wanted the gunshot effects to be as realistic as possible. In the scene where McClane is hiding under a desk and he shoots one of the terrorists, the bang was so loud that it actually caused permanent damage to Bruce Willis' hearing.
The movie was Alan Rickman's film debut.
The "German" the terrorists are speaking in the theatrical version is just gibberish. Most of the terrorists’ dialogue is incoherent gibberish that was later fixed for the VHS release. Only Alan Rickman actually spoke German in the movie.
Bruce Willis wasn’t on the original poster. Back in 1985, exploding buildings were all the rage and Bruce Willis was just another television actor. The studio had concerns that his image might prevent box office success because he wasn’t a proven movie star.
The Hans Gruber-Bill Clay scene was added to the script after shooting had already begun. Producers wanted a way for McClane and Gruber to meet prior to the climax and added it in after hearing Rickman’s American accent
Nakatomi Tower is actually 20th Century Fox’s headquarters. One would think that filming in your own office would be a smart way to trim the budget, but the studio charged itself rent to shoot there.
The movie had to be filmed at night. Willis was busy filming the TV series "Moonlighting" during his days and was only available at night.
“Yippee-ki-yay, motherfucker!” is a piece of movie history. The line has been used by John McClane in all five movies and was voted as #96 of “The 100 Greatest Movie Lines” by Premiere in 2007.
Willis landed his part in 12 Monkeys thanks to Die Hard. 12 Monkeys director Terry Gilliam cast Willis for the part based on his improvised lines during the scene where he pulls broken glass shards out of his foot. Willis actually wore a pair of rubber feet while running through the broken glass. Look close enough and you’ll notice that his feet look unusually Hobbit-sized.