Currently entertaining the notion that the whole reason the bros became plumbers wasn't because it was Mario's idea or because it was something they both wanted from the get-go, but because of Luigi.
Mario's the kinda guy who wants to try everything at least once. As soon as he's able to start picking electives in school, he has a blast choosing some new endeavor to undertake each semester. Luigi doesn't have much confidence in his own abilities, he doesn't really think he's good at much of anything, but failing stings a lot less when his brother's there to support him and laugh about it with him, so he enrolls in whatever Mario enrolls in and follows in his every step.
And that's how they both end up in a plumbing class their junior year of high school. They're both handy, they come from a blue-collar family, they know that's probably the same route they'll be taking after graduating (and they took the general prereq class last semester anyway), so maybe it's a given they end up there, but that doesn't even factor into the decision when it happens. They're still kids: Mario thinks it sounds fun and Luigi goes wherever Mario goes, and that's all there is to it.
And it clicks with Luigi. Mario's good at it, of course he is, he's at least decent in just about everything, but it's just one thing out of a thousand he can see himself doing. But nothing has ever come so naturally to Luigi as this has. Plumbing, of all things! He's never enjoyed something so much for its own merit, rather than the merit of sharing the experience with his brother, and it gives him a sense of confidence and identity that's almost alien in how unexpected it is.
But he's still Luigi, younger, shier, more awkward Luigi, and he still has no idea how to navigate the world without his brother by his side, and frankly, he's not sure if he wants to. He'd happily give up this newfound love of his to keep following Mario. Mario knows that better than anyone. And he's not about to let that happen.
Plumbing's fun enough, he figures, he wouldn't mind sticking with it for good. And watching his timid twin brother become brighter and bolder, if only when he's got a wrench in one hand and a plunger in the other, is enough to stoke that casual interest into a true passion, and enough to turn this random endeavor into a shared dream.
Just... Mario following Luigi for once instead of the other way around, c'mon. 😭
