Waluigi is Luigi's "evil twin". He is a heavy character and drives large vehicles only.
Waluigi is the same age as Luigi. He is Wario's brother, and is Mario and Luigi's cousin. He has a purple hat and gloves with an inverted L (Γ). Waluigi is unlocked from the beginning of the game.
He has appeared on the most recent games from Mario Kart series. The Mario Kart: Double Dash!! course Waluigi Stadium was revamped and is part of the Mario Kart Wii Banana Cup.
Acceleration +6, Drift +5, Off-road +3.
Mario Tennis series
Mario Tennis is the first game that Waluigi appeared in. He was made so Wario would have a partner. He is a Technique character, and has good control and reach, but bad power and speed. In Mario Power Tennis, Wario and Waluigi face off against Mario and Luigi in the first round of the tennis tournament. Mario and Luigi defeat them. They later vandalize Mario and Luigi's pictures in Peach Dome to get revenge. They nearly get arrested, and form an alliance with Bowser. He is a Defense character, with great reach, but low movement and power. He can use the Whirluigi and the Swimming Return. In Mario Tennis Open, Waluigi is a defense character, and is pretty much unchanged.
Mario Party series
In Mario Party 3, Waluigi is playable in multiplayer mode. He also steals the Star Stamp, and if the player makes it through Waluigi's Island, he will give it back. In Mario Party-e, he appears in a few mini-games, like Waluigi's Reign, Time Bomb Ticks!, and has two cards, Waluigi and Super Waluigi. They are both duel cards. In Mario Party 7, Wario and Waluigi share the Vacuum Orb that can steal other characters' coins. He is also playable in Mario Party: Island Tour and Mario Party 10.
Mario Golf series
In Mario Golf: Toadstool Tour, Waluigi is a default playable character. His maximum hits are 209 yards. He has good impact and spin, and average shot height and control. In Mario Golf: World Tour, he is a playable character and has a purchasable club for Miis to use.
Mario Kart series
In Mario Kart: Double Dash!!, he is a default playable middleweight character. His default partner is Wario. His kart is the Waluigi Kart, and his item is the Bob-omb. His course is Waluigi Stadium. In Mario Kart DS, he is an unlockable playable character. He is a middleweight, and his karts are the Standard WL, the Zipper, and the Gold Mantis. His course is Waluigi Pinball, which is one of the most popular Mario Kart courses. In Mario Kart Arcade GP 2, he is a playable all-around racer. Waluigi Stage is his cup, and it includes Stadium Arena and Waluigi Stadium. In Mario Kart Wii, he is a default playable character. He is a heavyweight racer. He has good acceleration , drift, and off-road. Waluigi Stadium is a course in Mario Kart Wii. In Mario Kart Arcade GP DX, he is an unlockable playable lightweight character. In Mario Kart 8, Waluigi is a default playable heavyweight character. He has good acceleration, handling, and grip, and is one of the lightest heavyweights.
The flipped letter "L" (Γ) on his cap is also the (Upper Case) Greek letter gamma.