Seinvocc

Chao Race

Simply enter the waterfall cave in the Neutral Chao Garden and take the right path to enter the Chao Race section of the stadium. Here, one can enter a chao of one's choice (one from any of your gardens) in any available race for prizes! In stead of Emblems, though, certain feats will yield special prizes of their own. To host or join a Party Race (multiplayer against each other, rather than default NPA chao), simply make or join a thread that has "Party" in its title. Party Races won't usually yield prizes of their own, though nothing is stopping characters from gambling on their own.

Chao Karate

Read the Chao Race description, and this is pretty much just the same. You take the left path, and multiplayer matches are called "Versus" matches.