I would add a little more cat themed stuff to the game, some examples;
1. The main menu - Have a bag of cat food with the cat sitting next to it and on the bag have the options for 'Single, Multi, Controls, Settings, Quit' on it making it look like its part of the bag's design and fit the rest of the toon theme
2. The speedometer could be shaped like a cat paw in a toon style like the rest of the game. The current one kind of clashes with the style. The lap, best time etc transparent bars looks fine. I'd add MPH/RPM to the speedometer for added humor