This is one of our favorite things to do! Usually if you ask the CM who is outside of the doors where you enter for the class (they come out a few minutes before they open the doors to everyone) they will tell you which character they will be drawing. Some are easier to draw than others. I agree though, with the not so well known characters being drawn...it's hard for anyone to draw them and visualize it if they are not familiar with what they look like, especially for kids. Not that the CMs should have to customize the class to the demands of the people always, but they should stick to the more well known characters. Theres tons of them!
Have FUN~! It's a great souvenir!