Doom 3 (Remake)/References

Doom

 * The entirety of the original Doom is unlockable as a side-game via inputting the password "ULTRAVIOLENCE" as the opening password to the computer in Sergeant Kelly's bunker. The game itself is modified significantly from the original.
 * There are twelve new weapons, bringing the number of weapons available to the player up to just over double the original amount: the Axe, based upon the weapon from Doom RPG and used as both an alternate melee weapon that can kill the lightest enemies in a single hit or break down certain doors (equipped under weapon slot 1 with the Fists); the Auto Pistol, functioning like a faster version of the HacX pistol and resembling the unused gun seen on the original cover art (equipped under weapon slot 2 with the Pistol); the Machine Gun, based on the scrapped concept from the original game and functioning similar to the machine gun in the main game (equipped under weapon slot 4 with the Chaingun); the Unmaker, a scrapped weapon from the game's planning stages that was later included in Doom 64 that functions akin to a railgun and does not possess ammo pickups, instead gaining shots by killing enemies (equipped under weapon slot 7 with the BFG 9000); the Grenades, which function similar to the grenades in the main game (equipped under weapon slot 8); the Fire Extinguisher, based on the Doom RPG weapon that is used to extinguish fires to allow access to certain secret areas as well as damage certain enemies such as the Pain Elemental (equipped under weapon slot 8 with the Grenades); and the Dark Claw, another scrapped concept from the beta of the original that functions as a continuous beam of mid-range highly damaging energy with no individual ammunition, instead slowly draining the player's own health to power it (equipped under weapon slot 10 with the Chainsaw). In addition to this, the Super Shotgun from the second game is now available.
 * If played on "Nightmare!" difficulty, the game will be darker and use the PlayStation Final Doom soundtrack.
 * The Backpack is redesigned to resemble the backpack in the main game, which is in turn a updated retooling of the original design.
 * The Super Turbo Turkey Puncher 3 game, which uses the fist sprites from the game, is retained.
 * The famous IDDQD (god-mode) and IDKFA (all-weapons) cheat codes can be entered in-game. Doing so will instantly kill the player with the message on-screen of "Trying to cheat, eh? Well, now you die!", award the player the "Nice Try!" hidden achievement and send them back to their last checkpoint save.
 * Secret Level 33, the final secret level of the game, is a recreation of the legendary first level of the game, Hangar, also known as E1M1.
 * The "Nightmare" difficulty was originally the hardest difficulty of the game and Doom II, but is instead the second-easiest difficulty of the main game.

Doom 64

 * The uniform armour worn by the Marines resembles the armour worn by the protagonist of 64 with some elements from the armour worn in the original Doom 3.

DOOM Eternal

 * A advertisement for the game pokes fun at Eternal with its tagline "No magic swords. No useless arm blades. No ugly, overcomplicated, edgy Tolkien wannabe stories. No backstabbing AIs, and no puke-green heavy metal Warhammer 40k rejects. Welcome to the real word, bitch." The humour of this is ironic, as all these events appear in-game.

References to Other Doom Fanworks

 * The famous Hissy plush Cacodemon, made by Jonas Feragen, appears in Sergeant Kelly's personal quarters on his bed.
 * The infamous "so bad it's good" fanfiction Doom: Repercussions of Evil is referenced by the Imps writing on the walls in blood "JOHN IS A ZOMBIE", "YOU WILL BE KILL BY DEMONS" and "YOU ARE THE DEMONS".

References to Other Games

 * The secret levels of the game, with the exception of the first, second, fifth, tenth, twenty-fifth, thirty-first, thirty-second and thirty-third, are all recreations of levels in past first-person shooter games.
 * Secret Level 9 is a heavily modified recreation of the Team Fortress Classic version of the Team Fortress series' iconic map, 2Fort. Its placement is also a reference to the main number of classes in the games.
 * Secret Level 14 is a recreation of the seventh level of the fourth episode of Quake, Azure Agony. Its placement is also a reference to the original size of the file, 1.4 MB.
 * Secret Level 30 is a recreation of Spaceport from Duke Nukem 3D 's second episode. Its placement also references the game's subtitle, with the number 30 standing in for the word 3D.
 * The famous Dopefish from id Software's Commander Keen series appears on the front cover of a book on the desk in Sergeant Kelly's personal quarters.