King Boo is a large weight character in Mario Kart Wii. He is the leader of all the Boos.
Handling +5, Off-road +3.
Luigi's Mansion series
Before the events of Luigi's Mansion, Professor E. Gadd captured Boolossus and put him in a Mansion.
Super Mario 64 series
In Super Mario Sunshine, King Boo is the leader of the Boos on Isle Delfino. He is a boss in Sirena Beach. If Mario defeats him, he can save Luigi.
Mario Kart series
In Mario Kart: Double Dash!!, he is partners with Petey Piranha.
Mario Party series
In Mario Party 8, he gives out Stars on his board, King Boo's Haunted Hideaway. Players can also purchase Boo.