Have you ever ridden on a unicycle, with only one wheel?
I haven't I once had a friend who did that though!
Unicycle
A unicycle is a vehicle that touches the ground with only one wheel. The most common variation has a frame with a saddle, and has a pedal-driven direct drive. A two speed hub is commercially available for faster unicycling. Unicycling is practiced professionally in circuses, by street performers, in festivals, and as a hobby. Unicycles have also been used to create new sports such as unicycle hockey. In recent years, unicycles have also been used in mountain unicycling, an activity similar to mountain biking or
action, Niven eased their nervousness by telling them, "Look, you chaps only have to do this once. But I'll have to do it all over again in Hollywood with Errol Flynn!" Asked by suspicious American sentries during the Battle of the Bulge who had won the World Series in 1943, he answered, "Haven't the foggiest idea, but I did co-star with Ginger Rogers in "Bachelor Mother"!" 
Niven ended the war as a lieutenant-colonel. On his return to