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.
“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”
It turned into Banjo Kazooie: Nuts and Bolts