I'm a sucker for the real number system :) I love offering extra credit for this topic. Here is a cute idea based on a theme I did many posts ago titled "Pin The Tail On The Real Number Donkey". A student of mine had the same idea and her donkey looks better than mine. The only flaw is that her 'irrational' circle is mixed with the other 'rational' circle. It's still a cute project though!