After the old motorbike demostation it starts, the demo will be relevant .

Note the (assumed) husband and wife running on the wheels at the end haha.

Best explanation i have ever found, and a bit of fun

http://www.youtube.com/watch?v=K4JhruinbWc 

Chris.

Nice video. I've seen it before, and I already know how a differential works, but it was still worthwhile to watch!