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 six new weapons: 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 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 Grenades, which function similar to the grenades in the main game (equipped under weapon slot 9); 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 9 with the Grenades); 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 10); 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 Unmaker).
 * If played on "Nightmare!" difficulty, the game will be darker and use the PlayStation Final Doom soundtrack.
 * 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.
 * The final secret level of the game is a recreation of the first level of the game, Hangar, also known as E1M1.

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 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.