In-universe, "Mazes and Monsters" is a Shoddy Knockoff Product of Dungeons & Dragons
Both Mazes and Monsters and Dungeons & Dragons exist in the film's universe, but the former has somewhat different rules, hence why there are so many differences between the game and the real-life Dungeons & Dragons. Mazes and Monsters initially became popular on college campuses, probably because it was cheaper and/or caught on with students who thought Dungeons & Dragons was "too mainstream," but ultimately failed to take off due to the number of annoying gameplay mechanics, such as not being able to resurrect dead characters and restrictions on being able to create your own campaigns.
"Mazes and Monsters" is the prequel to Bosom Buddies
