Check out the Lost Media Wiki’s article on Banjo-Karting/Banjo-Kazoomie!!
Banjo-Kazoomie was a prototype for the original Xbox that started at Rare Ltd. in 2004. In the prototype, players were able to construct their karts out of different parts to race. After it was cancelled, the concept evolved into Banjo-Kazooie: Nuts and Bolts, which was released on Xbox 360 four years later.
Before the cancellation, Brendan Gunn talked about the game in a interview:
“I’ve always wanted to do a racing game. I got to spend two weeks working on a prototype racing game for the Xbox. It was codenamed ‘Banjo-Kazoomie’, and it was a kind of kart racer, but you constructed the karts out of different parts, so I guess it was kind of a precursor to ‘Nuts & Bolts’. But for those two weeks I was doing the driving mechanics for it”
Only 3 footages and a clip were available on the Internet.