Luigi is very timid, anxious, and less willing to jump into danger than Mario. In this pitch, Mario and Luigi's arcs reverse over the course of the film. Mario starts out wanting more than just being a plumber, and Luigi (not yearning for adventure the same way Mario does) just wants things to stay the same. But by the end, after Mario gets the chance to be the adventurer he's always wanted to be, something happens that makes him think he failed. He doubts himself thinking he'll never be more than just a plumber, so it's Luigi that encourages him to get up. Mario learns that he can be more than who he is while holding onto what he already has, and Luigi learns to embrace his new hero identity and is made braver as a result.

Like with Mario, I'm not looking for a spot-on impression. Just something mid to low range akin to Charles Martinet's performance, with either an Italian or New York accent, but also erratic, nervous, awkward, and innocent.