Crossovers

Crossover fiction is an instance where Doom and other universes collide. Most instances of crossover fiction with Doom are fan-made. Fans have made movies and games that combine elements of Doom and other universes together.

The most famous example of crossover fiction of Doom and another universes are 2 versions of Wolfendoom which are basically vice-versa of one's graphics being used on another game engine (i.e. Wolfensetin being used with Doom).