Mario Bros. is a platformer and the second game to star Nintendo's mascot Mario as a playable character. It also introduces Mario's brother Luigi and the idea of their occupations as plumbers. With one or two players, the objective is to clear the underground levels of enemies that are coming out of the pipes. This is done by hitting the platform they're on from below to flip them over, where they then can be kicked off into the water.

For this run, Spikestuff chooses to play only as Mario and cleans the pipes and sewers until the game starts looping, which is after 18 phases, doing so in record time.