Mario is a famous hero in A day with Bowser Jr, and is the Koopa family's (specifially Bowser) rival. He is worshipped by Nerdy and the Mario Fan Club. As a character, Mario appears in Two Koopas for a Throne Part 3, fighting with Morton Koopa Jr.
Mario is in a continous rivalry with Bowser, and the two always battle, Mario always winning. He is worshipped by the Mario Fan Club, a group of kids led by Nerdy who unite in a building and wear Mario's typical videogame outfit in his honor. He is not welcome in the airship, as any Koopa standing on top of it will attack anyone wearing his outfit (thinking that said person is Mario).