After a debate about speed between Orange Balloon and Mouse gets Mouse claiming that a bike is the fastest thing on wheels, the narrator takes us for an in-depth look at bikes. We learn that bikes make sense as a vehicle because of the way they exercise our bodies and also are designed to fit us comfortably. We learn that early bikes were so rickety that they were called ""bone-shakers,"" but today's bicycle is a near perfect machine. We see that some bikes are hand-made, but these custom-built bikes cost three-four times the price of ordinary bikes. Most are built in factories on an assembly line and we're taken inside one to see how it works. Mouse then watches a bike-racing show, but the narrator changes the channel to a hockey game because it's time to learn about how hockey pucks are made. We visit another factory, where we see various materials being mixed into rubber. Afterwards, a machine called an extruder shapes the rubber into sticks, which are then cut into the shape of a puc