Banjo X (sometimes stylized as Banjo-X) is a cancelled remake of Banjo-Kazooie that Rare developed for the Xbox sometime in the mid-2000s. The game was eventually scrapped and redeveloped into Banjo-Kazooie: Nuts & Bolts. Not much is known about the game aside from what was shown from a Rare Revealed video and some Twitter posts from Steve Mayles and Ed Bryan. Banjo X presumably did not go far into development before switching to vehicle-based gameplay, and ultimately Banjo-Kazooie: Nuts & Bolts.
The main idea behind Banjo X was for it to be advertised as a remake with minimal changes, in a similar vein to Conker: Live & Reloaded. However, the game would change drastically as the player progressed. The characters would be self-aware of being in a remake and would change their behavior accordingly. In the Rare Revealed video, Gregg Mayles cited Conga as an example of this.
Humba Wumba would have appeared somewhere in the game, even though her debut was in Banjo-Tooie. She and a couple of other characters were modeled by Ed Bryan, including Mumbo Jumbo, Tiptup, a Jinjo, and a "Bully". The Mumbo animation, circa 2004, was used to test if the lipsyncing would match up to the characters' mumbling.
The art style for Banjo X strongly resembled the block-shaped art style in Banjo-Kazooie: Nuts & Bolts. Ed Bryan even mentioned that they attempted a smoother, higher-polygon approach at first, but they decided to scrap it because they felt that it did not retain the charm from the original games.
Various unused models from this cancelled game were shared on Twitter by developers.