A game that was in development by Rare when Microsoft bought them out, Diddy Kong Pilot for the GBA was eventually retooled and released as Banjo Pilot. Some savvy collectors of RareWare goodies managed to come across the beta cart and dump it. It's playable, and obviously very similar to Banjo Pilot. As mentioned in the title, I can't link to it. You'll have to find it on your own if you're interested.