Check out this photo:
Image via National Geographic
That isn't Photoshop-ped, fellas. That is the photo of a two-faced cat from Massachusetts named Frank And Louie. The 15-year-old feline was the Guinness Book of World Records' longest-surviving "Janus cat" before it passed away last December 4, 2014.
What's a Janus cat? Named after the two-faced Roman god, a Janus cat is a cat that is born with the extremely rare genetic condition known as "diprosopus." The condition isn't a case of conjoined twins, wherein a fertilized egg splits but is fused back together by stem cells. In the case of diprosopus, well, we'll let National Geographic handle the explanation:
"Janus cats may have too much of the sonic hedgehog (SHH) protein, which plays a role in forming an animal's face during development. In some experiments, chick embryos exposed to an excess of SHH were born with two beaks and eyes spaced far apart."
Additionally, the said protein's role is to organize the brain and other parts into two halves. In the case of a Janus condition (it can also occur in other mammals including humans), the splitting into halves don't stop, thus resulting into two faces which share just one brain.
Now, you're probably wondering: "Is SSH named after the videogame Sonic The Hedgehog?" Yes, you are correct game-geek. Harvard itself confirms this, and credits the naming to a molecular scientist that had fallen in love with the Sega game while doing his research.
While most Janus cats don't survive more than a few days, Frank And Louie was lucky for two reasons:
1) The cat was adopted by a certain woman named Marty Stevens after it had been lined up for euthanasia as a kitten. She cared for the feline, resulting in a remarkable 15-year run.
2) Only one face could eat. Frank and Louie only had one functional esophagus and jaw, thereby minimizing chances of choking.
Learn something new every day, fellas! #YeahScienceBitch