Frank Sinatra could have been John McClane.
Ol' Blue Eyes had first dibs on the role that made Bruce Willis an action star. Die Hard is based on the 1979 crime novel Nothing Lasts Forever, which was a sequel to the 1966 book The Detective. The famous crooner turned actor starred in the 1968 film adaptation of The Detective and was therefore offered the chance to reprise the role of John McClane in the follow-up. Of course, Sinatra was already 73 by then, and said no.
Bruce Willis wasn't even the second or third choice...
At one point Clint Eastwood considered starring in a movie version of Nothing Lasts Forever. As the project developed, a number of man's man actors reportedly turned down Die Hard: Sylvester Stallone, Robert De Niro, Harrison Ford, Nick Nolte, Mel Gibson, Richard Gere, Don Johnson, Burt Reynolds, and Richard Dean Anderson.
Die Hard was Alan Rickman's first feature film.
Though he'd done television, including Shakespeare for the BBC, Alan Rickman had yet to star in a feature film when he was cast as Die Hard's main villain, Hans Gruber. Reportedly, Sam Neill passed on the gig. Die Hard's casting director offered the role to Rickman after seeing him in a stage production of Dangerous Liaisons.
That Teddy Bear should get an agent.
The teddy bear we see John McLane bringing for his kids for Christmas belonged to John McTiernan. The director used it again in 1990's The Hunt for Red October.
Die Hard is the reason Bruce Willis says 'What?' a lot.
Director John McTiernan favored extra loud gunshots, which is just one of the many details that made Die Hard look and sound so much more real than most action movies of its day. Unfortunately, during the scene where McLane shoots a bad guy from under a table, the loud bang of the blanks left permanent damage. As Willis explained to The Guardian in 2007, "Due to an accident on the first Die Hard, I suffer two-thirds partial hearing loss in my left ear and have a tendency to say, 'Whaaa?'"
Bruce Willis wore rubber feet.
It's one of the coolest moments in Die Hard. Hans knows McLane is barefoot so he orders one of his goons to "shoot the glass." To be extra safe during the ensuing scene, Willis was outfitted with a pair of rubber feet to wear over his real feet.
Sgt. Powell may as well have been Sgt. Johnson.
There's a Harvey Johnson and of course two different FBI Agent Johnsons in Die Hard. This was apparently a well-intended goof on actor Reginald VelJohnson, who played McLane's Twinkie loving patrolman pal and last minute savior, Sgt. Al Powell.
Alan Rickman hated that fall almost as much as Hans.
Director John McTiernan pulled a dirty trick on the late actor in order to achieve the look of terror on Hans Gruber's face in what became one of Die Hard's most famous scenes. Rickman expected a one, two, three count before getting dropped 40 feet. Instead, he was dropped a second early. It's that first take that's in the finished film.
Die Hard's enduring catchphrase was improvised.
It doesn't feel like a Die Hard movie unless John McLane says you-know-what, even when the f-bomb gets clipped by a PG-13 rating (as it was in 2007's Live Free or Die Hard). Willis himself said he improvised the line, which is a modified version of a line made famous by the late King of the Cowboys, Roy Rogers. "It was a throwaway," Willis said in 2013. "I was just trying to crack up the crew," he told Ryan Seacrest. "I never thought it was going to be allowed to stay in the film."
Die Hard launched a bunch of imitators.
After Die Hard became a smash in 1988 it became a template for a slew of imitators, a whole subgenre of films that took the formula of relatable lone everyman badass against a a bunch of bad guys in a confined space. Die Hard 2: Die Harder was basically Die Hard in an airport. Hollywood also gave us Under Siege (Die Hard on a battleship); Under Siege 2: Dark Territory (Die Hard on a train); Passenger 57 (Die Hard on a plane); Cliffhanger (Die Hard on a mountain); Sudden Death (Die Hard in a hockey rink); Meltdown (Die Hard in a hotel); Skyscraper (Die Hard with a female hero); Air Force One (Die Hard on a plane, again); Paul Blart: Mall Cop (Die Hard in a shopping center); and Home Alone. Seriously, it's basically Die Hard in a kid's house.