Banjo-Kazooie Legend of the Crystal Jiggy is a fan-made ROM hack, adding a new storyline or quest focused on a "Crystal Jiggy." It's not from Rare but from the ROM hacking community.  Gameplay would involve searching for the Crystal Jiggy, likely spread throughout existing or new levels.  This modification enhances the original gameplay with a new objective and potentially new areas to explore.

Banjo-Kazooie Legend of the Crystal Jiggy

Banjo-Kazooie Fort Fun V4.0