Sullivan's Ass (or Butt) is a popular gag in Nova and Sp00n's community. It was slowly becoming an internet meme, until the Dead Rising 2 (see history) lets play ended. Sullivan's Ass may make a return in Dead Rising 2 Off The Record, but this is just a rumor. The meme is making a return but this time in Nova's Nonsensical Saints Row: the Third with the gas (Sullivan's Farts contained in canisters) as revealed in Episode 48.
When the two were doing their Dead Rising 2 playthrough, they joked around about Sullivan, a main character in the game's, ass, similar to Nova's Talking Butt. During the playthrough, 'mutant zombies' were made by a gas, the two joked that it was Sullivan's poop stink. In Dead Rising 3, Sullivan made a return when Sp00n was making a joke about Sullivan having a dirty ass.