These little snakes have separate heads and tails, but a common heart.  Travel presents serious difficulties.

Amazing Siamese-Twin Snakes Have One Heart Between Them.

Siamese-Twin snakes one of nature's rarest freaks, were born recently to a diamond-back water snake caught by a University of Michigan zoologist.  The tiny reptiles have separate heads, tails, and spinal columns, being joined together only at the middle.  X-ray photographs however show that they have one common heart.  Their actions are not coordinated and they frequently get tangled up, when one want to head north and the other has a fixed ides about going south.