Conker's Bad Fur Day started out as a much tamer game called Twelve Tales: Conker 64. Around the time of its announcement, Rare had already made two similar games, Banjo-Kazooie and Diddy Kong Racing. They feared criticism for making another innocent platformer starring "cutesy" animals, prompting them to completely redesign the game for older audiences in 1999. Rare kept it under wraps after this announcement, but assured it was still in development until the revamp was formally revealed in 2000.

Development on "Twelve Tales: Conker 64" began around the same time as "Project Dream" (later "Banjo-Kazooie"), however work on the game was put on hold for a long time to focus on improving "Banjo-Kazooie" and other experiments.