Waluigi

Waluigi is an antagonist in the Mario series. He is a tall, gaunt, mischievous man wearing black overalls, a purple long-sleeved shirt and a purple hat with a yellow upside-down L. He has a large pink nose, thin mustache pointing upwards and blue bags under his eyes.

Waluigi is the self-proclaimed rival of Luigi, and is extremely envious of the latter's fame. Contrary to popular belief, Waluigi is not Wario's brother, but rather a persona made up to gain relevance in the Mushroom Kingdom. As such, he intentionally designed his own personality, name, and appearance to contrast Luigi's.

Birth
Although his birth circumstances are not known, Waluigi is not a star child, as evidenced by his absence from Bowser's plan in Yoshi's Island DS. This supports the statement that he is, indeed, not Wario's brother.

Before Mario Tennis
Fueled by envy, Waluigi spent a long time watching and studying Mario and Luigi from the shadows. During this time he would use his gardening skills to breed and release Piranha Plants in sewers in an attempt to sabotage the Mario Bros.

Waluigi is also shown to be skilled at tennis, often choosing to wield a tennis racket as his weapon, even when not in a tennis match.

Mario Tennis
After observing them and training, the perfect opportunity presented itself when the first Mario Tennis tournament was held. Waluigi entered himself, and claimed to be "Luigi's arch nemesis", teaming up with Wario to steal the brothers' fame.