Anyways, in an OCT, contestants are required to submit a reference sheet of their original character, along with an audition about their character entering this contest. The actual rounds involve contestants taking their opponents characters, including them in their entries, and drawing them in an entirely different style. I find it to be an interesting exercise in creativity, and will be attempting to participate in one.
If you would like to see examples of these contests, go to http://octfollowers.deviantart.com/ for a directory of current and past OCTs. The biggest in the past have been Endzone and The Colosseum.