Tanooki Mario is a power-up of Mario from Super Mario Bros. 3. He is found as a driver in the November DLC pack for Mario Kart 8, along with Link and Cat Peach. He also reappears in Mario Kart 8 Deluxe. He's also an alternate skin for Mario in Mario Kart Arcade GP DX.
Tanooki Mario is Mario in a tanuki suit. A tanuki is an animal found in Japan. The main body of it is reddish brown, with a tan belly. The tail of the suit is striped dark brown and reddish brown. The head is also tannish brown, and there is an opening for Mario to see through. He looks just like regular Mario with blue eyes, dark red hair, and a black mustache. There's a small cap coming out of the suit right above Mario's head, and it's color is tan, along with the ears of the costume. Mario retains his white gloves from is regular outfit, because those gloves are just to cool not to wear.
Mario Kart 8
Tanooki Mario appears as a downloadable character in Mario Kart 8, downloaded in the November 2014 pack as well as Link and Cat Peach. He is a middleweight driver and has his own vehicle, the aptly-named Tanooki Kart. Some of Tanooki Mario's trick animations include fluttering in place (referencing his ability to flutter in Super Mario 3D Land and turning into a Statue with a bandanna (a reference to the Statue Leaf).
On a side note, some of Tanooki Mario's voice clips are recycled from previous Mario games, including Super Mario Advance, Mario Golf: Toadstool Tour, and Super Mario Sunshine, among others.