Doom was originally going to be a video game adaptation of Aliens - Scontro finale (1986). Plans for that were scrapped in order to allow more creative freedom.
The various weapons Doomguy uses throughout the game are actually digitized versions of toy weapons that the developers bought at a toy store.
Due to the game's low system requirements, hackers make it a challenge to port it on various systems, especially those that are not designed for gaming. Among many other devices, they've managed to run this game on a printer, the Apple iPod Nano, a graphics calculator and even on a cash machine.
The rock band The Smashing Pumpkins used the sound of the rocket launcher in their song "Where Boys Fear To Tread".