Waluigi
He was made as a partner for Wario by the company Camelot in Mario Tennis and other Mario spinoff games and has no real story behind him. He is in Super Smash Bros. Brawl, Super Smash Bros. for Nintendo 3DS and Wii U, and Super Smash Bros. Ultimate as an Assist Trophy. Waluigi is known to be smarter than Wario, but acts sillier.