"Banjo-Tooie" was developed by Rare and designed by Gregg Mayles, who previously worked on "Banjo-Kazooie". Development of the game started in June 1998. Some features that were originally cut during the development of "Banjo-Kazooie", such as some of its worlds and a multiplayer game mode, were instead integrated into "Banjo-Tooie". An additional world set in a castle was planned, but due to time constraints, it was scrapped during development and assets from it were used in constructing Cauldron Keep. The game features roughly 150 total characters, including enemies and non-playable characters.