I was fooling around with a rolled up bill one time, and this just sorta came out. It reminded me of the snake/'serpent' from the cartoon strip B.C.

Start by rolling the bill into a tube. (Here are instructions for getting the bill rolled up that way. I use these tubes in the spider and eyeglasses as well.)

Fold back and forth until it looks like this. Really. While this one is laying on its side on the flatbed scanner, these little guys will actually stand up on a reasonably flat, level surface if you're careful making them.