Earthworms can move more than you might think. When there's a worm on the surface and you touch it, it may go through a whole series of spastic contortions as it tries to evade you and your hungry maw. Not too different from people, actually. Try sneaking up on a loved one and tapping his/her neck gently. You'll probably see similar gymnastics.
When I first saw this critter on top of the cedar mulch in the backyard rose garden, I thought it was a misplaced worm. It was writhing from side to side, apparently trying to find a patch of soft moist soil. My first thought was that I'd scoop it up and relocate it to a shady damp patch under some ferns. When I touched it, it leapt about 4 inches up in the air. Hmm. Rather energetic for a worm, but I guess there are Olympic-class athletes even in the Annelida phylum. After a little more wrestling, I got the thing in the palm of my hand, and finally took a closer look. Hey: that's no worm. It's the wrong texture, and it tapers too much, and why is the thick end sort of...raw-looking? It finally dawned on me that I was looking at the hastily discarded tail of a lizard. Five-lined skinks (Eumeces fasciatus) are very common around here, so I'm guessing that's what kind it was.
Some lizards will unattach a portion of their tails when they're being pursued--a sort of sacrificial rear-guard. The tail twitches and hops around all on its own in a most distracting way, allowing the more important parts of the lizard to escape. This one hopped and squirmed and rolled around for about 5 more minutes before relaxing into floppiness.
I never did see the lizard. I guess I was distracted.