One of our craziest efforts along that line was a simulation of the rocket sled sequence that opened that TV show. We used several truck tire inner tubes tied between two trees to launch us on our bikes at high speed into the very large sandpile that a housing contractor had left behind. Great fun, and the sand caused your bike chain to make some really weird noises--better than the motorcycle sounds of baseball cards, clothes-pinned on the chain stays and fork, flapping in the spokes.