Accidentally-Correct Writing: WarGames depicts the Defcon system accurately, with Defcon 5 meaning "lowest state of readiness" and Defcon 1 meaning "highest state or readiness", but according to Word of God, they thought they had it backwards.
When David is being chided into changing Jennifer's score at the arcade. He loses a ship while being distracted playing Galaga, but the lower left of the screen shows he still has three lives remaining, despite that there's a cutaway where David says "You owe me a quarter.", then the next cut is showing the Game Over gameplay statistics screen.
When WOPR is running through its nuclear war scenarios at the end, it has misspellings of Argentina, Israel, Palestinian, and Malaysian.
Also, the first scenario that WOPR runs is "US First Strike," followed by "USSR First Strike." However, the list that appears of scenarios played shows the order reversed.
Combined with Dr. Strangelove, Russia has a real automated system: the Perimeter system, also known as the Dead Hand. Officially, it is turned off in peacetime and only turned on in times of crisis, but is said to remain fully functional and able to serve its purpose whenever needed.
Hackers created programs to dial numbers in an area to search for modems as shown in the film. These programs became known as "wardialers", though these already existed before the film and were commonly called "demon dialers." As dial-up modems fell out of use, the practice evolved into "wardriving," looking for open Wi-Fi networks.
Inspiration for the Work: Lawrence Lasker was inspired by a television special presented by Peter Ustinov on several geniuses including Stephen Hawking. Lasker said, "I found the predicament Hawking was in fascinating – that he might one day figure out the unified field theory and not be able to tell anyone, because of his progressive ALS. So there was this idea that he'd need a successor. And who would that be? Maybe this kid, a juvenile delinquent whose problem was that nobody realized he was too smart for his environment." The concept of computers and hacking as part of the film was not yet present.
Life Imitates Art: A common "problem" for military simulations provides a simultaneously amusing and disturbing example. Machine learning systems tasked with simulating cold wars frequently come to the same conclusion that Joshua did: the whole situation is a waste of resources, and deescalation is the only logical solution.
The makers of the film weren't allowed access into the real NORAD for security reasons, so the Ominous Multiple Screens were a mock-up of what they thought it looked like. As it turned out, NORAD's interior was comparatively mundane, so NORAD commanders later remodelled it to more resemble the film's depiction.
The modems are museum pieces today (acoustic couplers were outdated even then), but were so cutting-edge for their day that the film was many people's first introduction to the concept. The film even featured the first cinematic reference to the term "firewall". Also, 8-inch floppies.
While portrayed as advanced (for a home computer), David's eight-year-old IMSAI 8080 was woefully obsolete at the time the movie was filmed. Even the humble C-64 was more advanced and was readily available at local department stores. DVD commentary reveals that this was a deliberate choice by the filmmakers, to show that David is using old obsolete gear that he may have bought at flea-markets, rescued from dumpsters, or bummed off his friends at the computer centre. A C64 would probably be his dream-system.
Word of God says Barry Corbin ad-libbed the line "I'd piss on a spark plug if I thought it'd do any good!"
The jeep accident as David, Jennifer, and Falken ram through NORAD's front gate was unintentional; the jeep was meant to keep driving right to the base itself and not flip over. John Badham left it in and filmed a shot of the trio running the rest of the way to the base.
Troubled Production: Production got off on the wrong foot, with director Martin Brest fired after only 12 days of production. Brest had been shooting the film like a dark spy thriller while producers wanted a lighter-toned adventure movie. After Brest's firing, Matthew Broderick and Ally Sheedy were terrified they'd be dropped next and this stiffened their performances. Replacement director John Badham needed to make some effort to loosen the two up and eventually succeeded by challenging them to a footrace with the loser being forced to sing a song in front of the crew. Badham lost and sang "The Happy Wanderer" to everyone's amusement and this loosened the mood for the rest of the shoot.
The original writer of the story said that he wanted Falken to be played by John Lennon, and Lennon was reportedly interested in the role. Lennon was killed before filming began.
The original director was Martin Brest, but only two of his scenes made it into the movie: David and Jennifer's meeting with Jim and Malvin, and David calling Jennifer at a phone booth in the middle of nowhere.
Stephen Hawking was originally approached to appear in the movie, but he declined because he didn't want the producers exploiting his disability.
In the original script NORAD ends up giving David a part-time job, and he works as McKittrick's assistant; just as McKittrick said he started out as Falken's assistant.
Kevin Costner was offered the role of Lt. Steve Phelps, but turned it down in favour of The Big Chill...where his part got cut.
for UNIX. It "simulates" the WOPR computer.