Bowser Jr.

Bowser Jr. (Koopa Jr. in Japan) is one of Bowser's children, along with the koopalings. He is the main villain of Super Mario Sunshine, posing as Shadow Mario for most of the game. He is also the primary antagonist in New Super Mario Bros. He will also appear as an antagonist in Super Mario Galaxy.

Other Games
He has appeared in other non-platforming Mario games as a playable character, these being;
 * Mario Golf: Toadstool Tour
 * Mario Kart: Double Dash!!
 * Mario Power Tennis
 * Mario Superstar Baseball
 * Mario Strikers Charged