In SLL Short: Retard Mario Gets Arrested, he reappears and spends most of his time making weird noises, dancing, and touching people. This spooked a large Goomba and Mario. Mario then called the cops and sent him to jail. When he was in his jail cell, he was freaking out as if he was scared. After this event, we never saw Retard Mario again.
He makes a guest star appearance in TT Movie: Mario as he fights Sonic over meatballs. He is suffocated by a pillow, until he is revealed to be alive at the end. He is voiced by Logan but only says Meatballs.
He is somewhat similar to the smg4 variant of mario,due to him also being retarded and based off his super mario 64 appearance.
The other reason for being an SMG4 Variant is the fact that there's a spaghetti with meatballs, with said image appearing in most SMG4 videos.