Mumbo Jumbo is a Shaman who uses the Tansformation abilty on Banjo and Kazooie in Banjo-Kazooie but his role is taken in Banjo-Tooie by Humba Wumba. In Banjo-Tooie, Mumbo Jumbo is a playable character who attacks by using his staff, and performs certain spells for Banjo and Kazooie. He will also appear in Nuts and Bolts as the main shaman, as well as a farmer in the Nutty Acres stage and a mechanic in Showdown Town. He is also a playable character in Banjo-Pilot.
By Link, info from BanjoKazooie Wikia