Although Diprosopus can be frightening, and perhaps looks like someone photoshopped a picture, this disorder is an all natural defect caused by a protien called the "sonic hedgehog homolog", or SHH, named after the video game character, Sonic the Hedgehog. The SHH protien plays an important role when creating another head during the embyonic development. Scientists have tested the protien by introducing pellets of SHH into chicken embryos. After the eggs hatched, there were chicks born with duplicate beaks.
Yet it can be dangerous owning a Janus cat. They can die either at birth, or at their 3-4 birthday. Most other people die young when diagnosed with Disprosopus.
Ditto the pig was born with two heads, also. He got pneomonia and died as a famous adult.