Doom... um... what can I say its awsome.
- There is a room with a swastika, being a refrance to an earlyer ID game Wolfinstien.
- In the level E4M1: Hell Benith there is the letters NIИ which is a refrance to Nine Inch Nails
- In MAP30: Icon Of Sin, after the player teleports into the huge room with the head of the final boss, a strange, unintelligible noise is played. This is stored in the Doom 2 wad file as DSBOSSIT, and if reversed it becomes a voice saying "To win the game, you must kill me, John Romero". The voice is shifted down in pitch and is that of John Romero himself.
- In the same level, John Remero's severed head on a stick features as the main boss creature, although the head is hidden behind the face of the final boss, and can only be approached with the no clip cheat. The player must indeed kill it in order to win the game.
- There are two secret levels in doom 2 they are modeled after two levels from Wolfinstien.