Waluigi is a character that is capable of spawning from an Assist Trophy to aid one of the fighters. Waluigi originally debuted in Mario Tennis for the Nintendo 64, where he acted as Luigi's doppelgänger, similar to how Wario is Mario's doppelgänger. Waluigi's relationship to Wario has never been officially confirmed by Nintendo, but they are often speculated to be good friends or brothers. Despite their relationship, however, Waluigi has never appeared in a Wario series title.
Waluigi has never made an appearance in a main stream Super Mario title, with his appearance limited solely to spin-off titles. Many of his appearances show him to be in love with the Sarasaland Princess Daisy. Waluigi's first major appearance was in Dance Dance Revolution: Mario Mix, where he worked alongside Bowser to steal the Music Keys from Truffle Towers.
In Jake's Super Smash Bros., Waluigi will spawn from an Assist Trophy and begin to run around. Wielding a tennis racket, Waluigi will savagely beat opponents, and sometimes stomp them into the ground to bury them before sending them flying with a mighty swing.
Ugh. That's Waluigi. He likes to participate in the Mushroom Kingdom's sporting events, alongside his... umm... friend? Brother? Umm.... Wario. Waluigi's pretty weird, and often gets the short end of the stick, since he hasn't even appeared in an adventure game yet.... except that dancing game.
