Mario in The Rise of Sqeegee 7
Mario is the mascot of Nintendo who first shows up in the Rise of Sqeegee series in The Rise of Sqeegee 5. He also serves as one of the protagonists in Weegee's Revenge. In the Rise of Sqeegee 5, he fights Sqeegee and is about to become victim to the Sqeegee Stare until Luigi interferes and stops Sqeegee. He later encounters Weegee whom he recognizes from the events of Weegee's Revenge and Weegee immediately tries killing him, only for Mario to wear him out in the end. Once they agree that Sqeegee is the bigger threat, they pursue Sqeegee in his rocket ship. At the end of ROS5, Mario fuses with Luigi into one and defeat Final Sqeegee. Mario has never shown any resentment towards Weegee afterwards, but Luigi is a different case.
Mario and Luigi both return in The Rise of Sqeegee 6, though they don't fuse this time. In it, they engage Fire Sqeegee in a Pokémon battle featuring references to characters like The Mario Head Army and Budgeegee. Eventually, Wario crashes the battle, only to be killed by the Sqeegee Stare. Mario and Luigi are both defeated when the original Sqeegee separates from Fire Sqeegee and the two kick Mario and Luigi away.
Mario's latest appearance in the series was in The Rise of Sqeegee 7, where he and Luigi fused into Russmarrs2 again upon learning that Sqeegee has returned. Unfortunately, they accidentally break the forced fusion between Final Sqeegee and Hyper Sqeegee that had occurred in the previous episode, and after a retarded cameo involving Toad, the two Sqeegees fuse into Uber Sqeegee and absorb both Russmarrs2 and Suteegee X.4 (who had just arrived at the scene). Later, Russmarrs2 is freed when Suteegee X.4 pierces through Infinity Sqeegee from the inside. Russmarrs2's final role in the episode is powering up a Kamehameha alongside Goku and Meweegee to end the vengeance-seeking Suicide Squidward once and for all. It is assumed that Russmarrs2 unfused after the events of this episode, and Mario has yet to appear since. However, the creator has mentioned potential plans for a Mario return in The Rise of Weegee, considering his brother Luigi has already returned in a flashback.