I’ve seen articles claiming that Kids These Days find Luigi more relatable than Mario because he’s a goofy loser, but I think that’s a superficial reading of what makes his character tick.
The thing about Luigi is that when you look at what he’s actually capable of, he’s totally not a goofy loser - he just get treated like one with no particular justification.
He’s ever inch the unstoppable badass that Mario is, but he gets absolutely zero respect or acknowledgment for it because Mario is more photogenic and has better PR.
Basically, Luigi is a stark illustration of the fact that talent and hard work have nothing to do with actual success: you can work twice as hard and accomplish twice as much and fail to receive half the recognition of somebody who just happened to be in the right place and know the right people.
In Luigi’s Mansion, it is possible to see the moon in some outdoor areas of the mansion. The moon is closer than it appears to be; in fact, it’s hovering slightly above the floor of the room Luigi is occupying.