I don't remember if this was posted yet but...
Programmer Brendan Gunn said this in regards to the Banjo kart game:
"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"
George Andreas had this to say:
"We had a coin-up for a while, didn't we? Mark [Betteridge] was working on a racing game. Can you remember? It was a long time ago now. The working name was 'Balls-Out', as in flat-out."
It's on rareminion and it is originally from the Retro Gamer article on Rare.