Random Trivia For This Title:
- While the line "Yippee-ki-yay, mother*$@^#%!" is used in all Four [Die Hard] movies, a gunshot masks the '*$@^#%!' part in the latest installment. It also translates in Urdu to "here eat this"
- Prints were sent out to UK cinemas under the fake name "New Hampshire" - a reference to the state's "Live Free or Die" motto and the movie's original title - in spite of the title being changed to Die Hard 4.0 in European territories.
- According to Bruce Willis and Director Len Wiseman in the DVD Commentary, the story originally involved McClane's son, Jack. Originally, he was supposed to be the computer hacker John has to deliver to the FBI. Eventually that idea was dropped and the hacker became the Matt Ferrell character. It was then decided to bring in his daughter Lucy to keep up the series continuity of McLane always having a personal stake in what happens in the story.
- This film addresses the apparent continuity error in earlier installments - McClane is afraid of flying in the first two films, but not the third. Here, he explains that he took flying lessons in order to "face his fears."
- The French title translates as Die Hard 4.0: Return to Hell.
- When Gabriel is talking to McClane over the phone and pulling up his information on the computer, Bonnie Bedelia makes a cameo appearance in the form of her character Holly McClane's driver's license photo. The photo appears as though it may be either a publicity shot from a prior [Die Hard] film or a still photo (i.e. family portrait) from one of the movies.
- Scott Speedman was Len Wiseman's first choice for the role of Matt Farell whereas Ben Affleck was Bruce Willis' first choice for the role. Willis wanted Affleck in order to recreate the chemistry between two characters previously accomplished in Armageddon
- The bad guy Thomas Gabriel points a gun at McClane and declares "On your tombstone it will say 'Always in the wrong place at the wrong time'." "John McClane is back in the wrong place at the wrong time!" was a tagline used for Die Hard 2.
- When McClane is driving toward the helicopter, he says, "You think a traffic jam, throwing a car at me is gonna stop me, huh?" Director Len Wiseman dubbed the last part of this line ("Gonna stop me"), imitating the voice of Bruce Willis.
- The film's climax originally involved McClane racing alongside an exploding gas pipeline on a motorcycle with Matt in a sidecar. The idea evolved into Gabriel trying to kill McClane and Matt by routing gas to their location through the pipelines.
- This is the first [Die Hard] film without the music of film composer Michael Kamen. Kamen died in 2003. Portions of Kamen's previous [Die Hard] scores, however, were incorporated into the score by Marco Beltrami.
- Director Len Wiseman credits actor Timothy Olyphant (Thomas Gabriel) with coming up with the idea of how McClane kills Gabriel. In order to keep it a secret, the scene was not included in the film's shooting script.