Doom Codes -

Features menu:
Enter ?TJL BDFW BFGV JVVB as a password. The game will begin on level one. Pause game play to access a new "Features" menu that allows level selection, invulnerability, map mode, health boost, and weapons/ammunition. You can also access the "warp to fun" levels 25, 26, and 27. Once enabled, the health boost and weapons/ammunition options may not be disabled. The invulnerability option will be disabled on level 32. Once enabled, the features menu will appear when any saved game is paused until the Nintendo 64 is powered off or reset.

Secret levels for special keys:
Level 4 has a secret entrance to level 29.
Level 12 has a secret entrance to level 30.
Level 18 has a secret entrance to level 31.
Destroy all the barrels on Level 1 to access Level 32. The warp is in a secret room behind the starting location of the level. Save the first barrel to be destroyed last.

Death messages:
Do not immediately resume game play after losing a life. Random messages will appear at the top of the screen for several seconds at one minute intervals.

Super status:
Enter W93M 7H20 BCY0 PSVB as a password. The game will begin on the last level with 100 health, 200 armor, all weapons, full ammunitions, the backpack, and levels 29 to 31 completed. The inventory will contain three pentagram items that power-up the laser to be three times as powerful as the BFG9000 and activate the three switches in the last level to close the gates that spawn the monsters.

Level 32 (Hectic) demo:
Enter RVNH 3CT1 CD3M 0??? as a password. A demo of level 32 will appear as the fourth demonstration sequence.