Two Headed Snakes

Each head of a polycephalic animal has its own brain, and they somehow share control of the organs and limbs, though the specific structure of the connections varies. Animals often move in a disoriented and dizzy fashion, with the brains "arguing" with each other; some animals simply zig-zag without getting anywhere Snake heads may attack and even attempt to swallow each other. Thus, polycephalic animals survive poorly in the wild compared to normal monocephalic animals.
Most two-headed snakes only live for a few months, though some have been reported to live a full life and even reproduced with the offspring born normal. A two-headed black rat snake with separate throats and stomachs survived for 20 years. A two-headed albino rat snake named "We" survived in captivity for 8 years. There is some speculation that the inbreeding of snakes in captivity increases the chances of a two-headed birth.
A famous successful modern case is that of the human dicephalic twins Abigail and Brittany Hensel, born in 1990. The twins have two separate heads and faces, they each have their own individual brains, spinal cords, and hearts. Abby and Brittany however have three lungs, and share all the other organs. Each twin controls the limbs and body parts on her "side", and with coordination that allows them to walk, run, play piano, swim, drive and do anything else they wish.