I didn't have my video camera on me that day, but here are some work-in-progress pics of Jim sketching Joker. Obviously, one of the more popular and fun characters for him to draw because of his extreme personality.
The only color markers on-hand were ones you had to apply water onto, so Jim quickly laid some water on the page and sketched out the general shape of Joker's head in green.
After he let it dry a little, he went back over it with a black marker and added some red and white highlights for those finishing touches.
Including drying time, this sketch took about 10 minutes.