This answer comes in simple terms.
They are the Mario Brothers. Therefore their last names are Mario. Seriously.
That's it.
Well Mario And Luigi Are the Mario BROTHERS So they're last names are Mario. So Mario's Full name is Mario Mario and Luigi's Full name is Luigi Mario
Myamoto
its is Mario as in the super Mario brothers. hi um no its really not that would make no sense Hey im luigis #1 fan and you're wrong Luigis and Marios last name is Gonzales so it's Luigi Gonzales and Mario Gonzales have a nice day!
Yamasaki? There names are Mario Mario and Luigi Mario.
Mario
mario is luigis bro
mario 3d land
no one knows yet.
silly! its Luigis mansion
No. They're more like Mario and luigis evil twins.
check the game guide on IGN...........its on the course Big Boo's Haunt :P
he has no last name.
marios brother is luigi and luigis brother is Mario wario and waluigi are there cousins
trapped in a portrait on the final level of luigis mansion