Luigi

"Yay! A Hoohoohoohoo." -Luigi, Mario Superstar Saga
"It's green idiot and Ms. Stupid. ATTACK!" -Roy Koopa, The Koopaling Adventures
"Wow, are you impersonating me, you stupid green monster?" -Luiga, The Koopaling Adventures
Luigi is a wonderful green guy in The Koopaling Adventures, and only appears in there.