His first appearance was after the scene where FightingMario54321, Ruffman8890 and MejiaCantilloGustavo end up in a prison-like room and before the scene where Mario and Kirby do a Pokémon battle. When he appears, Narrator thinks it may be the savior or some random guy spying on the audience. VidMaster then tells him to shut up.
Next, he enters the nightmare after Kirby uses Rave and tells the Mario Bros. to follow him. When Luigi asks who he is, he responds with "Uhh, not right now!" Mario then kills Kirby with Luigi. They then get to SuperMarioGlitchy4 and Xboxfan977, who are about to get mauled by zombies. After SMG4 and Xboxfan997 throw stuff at the zombies, ??? says to the Bros. that they're gonna need a guy that can blend in the crowd of zombies. Toad then appears and gets forced by Mario to help them, even though he has an appointment with Darth Vader.
When Toad comes to SMG4, the latter mistakes the former for a zombie at first, but then Toad tells to SMG4 it's him. They attempt to escape with Toad holding SMG4. Toad, thinking SMG4 is too heavy, let's go with an "ARRRGH TOUCHE!", and goes with Plan B: Running over the zombies with the Newgrounds tank while yelling, "WOOHOO! World domination!"
When MCGustavo accidentally cuts his leg, he screams which attracts the Bros. and ???'s attention. Luigi, needing a toilet break, enters the room along with Mario and ???, dismayed to find out that it was bad timing. ??? then says that they're gonna need an escape route. They're gonna need a "mega giga watt-machine" that can—MCG finds an emergency exit before ??? can finish his phrase, while SMG4 says to ??? that he said they're gonna need a MegaMan thing, much to ???'s disappointment.
The gang then goes back home via MCG's emergency exit. FM then asks what ???'s name is, but ??? responds with "I cannot right now... cause we still have business to deal with..." RM then says, "Well, at least he likes killing people".
Mario, SMG4, X, ??? and the rest of the gang then enter Bowser's Lair, where SuperMarioGlitchy3 is surprised to find SMG4 while Bowser is shocked to find Mario, engaging in a fight. Mario then starts running towards SMG3 but gets hit by a pan, forcing ??? to become his substitute and destroy the Nightmare Stone.
After going back to their normal lives, X tells ??? to tell them his name. However, he instead tells his quest to save the gang, in which he was walking when Navi the fairy appeared in front of him and repeatedly said "HEY LISTEN!" over and over again, causing him to kick the fairy, and get hit by a rock, making him mentally known what his quest was. ??? then says farewell to the gang and jumps into oblivion, never seen or heard of again.