I really wanna find out if we're gonna get that answer in the next Mario movie. Even though they were friends when they were kids and played sheriffs and outlaws, Wario's first appearance in sml2 is just so sudden that it feels like they've never met before. Wario is literally the antithesis of Mario to the point where it feels like he came from somewhere else and one day he just showed up, and they were even planning on making him German.
I feel like so many movies have a tendency to make every single encounter an introductory one, where history between characters specifically only gets revealed later to prioritize making them mysterious. Even with the Mario movie itself, they did exactly that when they retconned Rosalina's origin story and set it up so Peach gradually remembers they're sisters. So I feel like if Wario appeared, they'd be like "Oh yeah Mario and Wario go WAY back" and maybe we'd know if he grew up in Brooklyn or something
