Waluigi

Waluigi is a recurring character from the  series who first appeared as Wario's partner in Mario Tennis. He appears as a playable character in Super Smash Flash 2.

Character description
Waluigi has so far only appeared in Mario spin-off and party games, as opposed to the main platformer titles, save for a few cameos. He is Luigi's "evil" rival, in the same way that Wario is Mario's. Along with this, Waluigi has a hat and gloves with a "Γ" gamma symbol, which is similar to Wario's "W", which is also an inverse or an upside-down "M". Unlike Luigi's green hat and shirt, Waluigi has a purple shirt and hat with black overalls and orange elf-like shoes, while his Γ symbol is yellow. He is believed to be Wario's younger brother (though the game Mario & Sonic at the Olympic Winter Games on the Nintendo DS states they are not, saying that Waluigi is actually Wario's co-partner, despite the fact that he has never physically appeared in a WarioWare game, but as the game was mainly handled by SEGA, the authenticity of this is called into question) as well as one of his many friends. Waluigi was created by Camelot's Fumihide Aoki and is voiced by Charles Martinet, like Wario and both Mario Bros..

In Super Smash Flash 2
Waluigi is a newcomer character in Super Smash Flash 2. His reveal was shown during the Day 3 livestream at Super Smash Con 2018, development of the character did not start until after the convention had ended.

Trivia

 * In the  series, he, Isaac, and Krystal are not playable characters, being Assist Trophies instead.