I'd say the Kart game would most likely be Sonic and All Stars Racing 3, going by the description and Sumo having done the past ones. Plus, Nintendo not being listed as a partner, which would probably be the publisher if it was Diddy Kong Racing. It could be something like Microsoft Kart, Crash Team Racing, UbiSoft Kart or EA Kart to mess with me though since those companies are listed as partners and have global IPs from Halo to Rare's franchises to Gears for Microsoft, Rayman to Assassin's Creed from Ubi, Sony has Little Big Planet (which had a racer before) to Uncharted to other stuff, EA has Mass Effect, Plants vs. Zombies, etc. :P