In level 3 of episode 6, viewing the stage from above reveals that it is mostly made of swastikas.

The secret level of Episode 3 is a parody of Pac-Man complete with ghosts that damage the player when they touch him. Pellets are replaced with gold chalices and Power Pellets are replaced with extra lives, and there are some normal Nazi enemies in the level as well.

The most recent rerelease of the game on Xbox Live Arcade replaces the Pac-Man ghosts with Hitler Ghosts due to license issues.

The name of the two bosses 'Hans Grösse' and 'Gretel Grösse' are taken from the children's story 'Hansel and Gretel'.

ID software originally held a contest where, if a player completed the insane secret maze in Episode 2, Floor 8, they would find a sprite that said "Call Apogee say 'AARDWOLF.'" The contest was cancelled because map editors were made for the game that allowed players to navigate through the maze much easier, trivializing the contest. In later versions, a certain part of the maze was blocked off and/or replaced the sign with a pile of bones.

In the prototype version of the game, B.J. is wearing tan clothes. This was changed in the final version, where he is wearing grey clothes instead.

On the Macintosh version of the game, pressing B on the id Software logo will show a secret picture depicting a cartoon of lead programmer Rebecca "Burger" Heinemann getting decapitated by an axe-wielding unnamed member of management. This image also appears in the 3DO version of Out of this World.