Every now and then we see reports of animals born with extra legs or heads... generally they are the parasitic remains of what would have been a twin, where the egg fails to divide cleanly, or the foetuses become merged in some way...Most of them die, but some of them do live.. adapting to having two heads or six legs or parasitic parts...
Here is Lil'Bet - you can read more here
The most remarkable thing about this cat is that it appears that he not only has two faces, but also has two functioning brains. Even though no x-rays have been taken to confirm this, veterinarians think that the two brains function independently because one face can sleep while the other is awake, one face can sneeze while the other does not, and both faces eat and breathe.
Meet Frank and Louie... each side has a name. He was six years old when this was taken.
They have two mouths, two noses and two working eyes. "He" does have a third eye in the middle, but it is non-functional.
If you like this sort of thing - you can read more at Feline Medical Curiosities - Conjoined Kittens - or check out Feline Medical Curiosities- Facial Deformities