OMG. This Is Beyond Creepy. The Zombie Snail!

Yes, it does look like a snail.. but it's a worm, a parasite, Leucochloridium, that has taken over the body of the snail and is mimicking its movements so that birds are tempted to eat it. Then, the worm can lay eggs which the bird will expel, well, the normal way a bird expels stuff.. it IS rather pretty, but.. eew.