Pedaling appendages! It's the magically moving fingers!
How to do it
First, get a friend.
Have your friend make two fists with their hands and hold them together so that their knuckles and thumbs touch. Then, keeping their hands together, they should put their pointer fingers straight up so that they are pointing to the ceiling.
Now start pedaling your hands on each side of your friend's for about 30 seconds.
Look what happens! Your friend's fingers magically move together.