1. Drawing a lot of inspiration from film, one of the original programmers, John Carmack, claims DOOM (1993) was a cross between Aliens and Evil Dead.
2. The Aliens influence: The game started out as a licensed Aliens game.
3. The Evil Dead influence: There's a plot surrounding a demon invasion, the chainsaw is a playable weapon, and the original cover is very similar to the cover of the third Evil Dead installment, Army of Darkness.
4. According to John Carmack, the game's title was taken from the Tom Cruise and Paul Newman film, The Color of Money.
5. In the newest DOOM (2016), there are secret doors that will lead you to sections of maps from the original game, complete with the original textures, pickups, and enemy locations.
6. Doomguy is available as a secret skater in Tony Hawk's Pro Skater 3's PC release.
7. In 2004, a DOOM board game was released. It was fairly well-received, with a 6.4/10 Board Game Geek Rating.
8. In Tomb Raider III's "Nevada Desert" level, unarmed guards are wearing jackets bearing an image of one of DOOM's lost souls.
9. The newest DOOM is loaded with cool easter eggs. One in particular is a nod to Terminator 2 and it's triggered when you die in a pit of lava.
10. The original DOOM was so influential that it spawned an entire generation of first-person-shooters that, at the time, were simply labeled, "DOOM clones."
11. In a Season 16 episode of The Simpsons titled, "Midnight Rx," Homer goes to see a job consultant who's playing DOOM.
12. The 2005 DOOM film has a character named Todd Carmack. The original DOOM production team had a programmer named John Carmack and an artist named Adrian Carmack.
13. In the 1997 Simpsons game, Virtual Springfield, there's a DOOM-influenced mini-game called "Apoom" in which you play as Apu clearing the Kwik-E-Mart of bullies.
14. In 1995, due to the popularity of the game and to promote Windows 95, Bill Gates superimposed himself into DOOM and killed a demon with a shotgun.
View this video on YouTube
15. DOOM was originally supposed to use a "player lives" system where, when you run out of lives, you are forced to start over. They decided it would be too frustrating and opted instead for a save/load system.
16. In Duke Nukem 3D, you'll encounter a dead man who looks suspiciously like the Doomguy. Duke will even say, "That's one doomed space marine."
17. And in January 2016, John Romero tweeted out a link to a brand new level he designed as part of the original DOOM that can be downloaded and played for free.
It's been 21 years since I made a DOOM level. Here's my version of E1M8 using DOOM1.WAD. https://t.co/ueKM7gBbXd