You're not seeing double. A young cow calf with two faces became the longest living example of the rare genetic mutation in late October, passing the previous calf record of 40 days, Caters News reports.
Watch: Lucky the two headed calf from Kentucky
The calf, known as Lucky, lives on a farm in Campbellsville, Kentucky. Owners Brandy and Stan McCubbin told Caters they have come to love the calf and "treat it like their baby," although they were surprised by its unusual appearance when they first saw it a few weeks ago.
"It's something I've never seen before and I think it's amazing," Stan McCubbin told local news station WDRB.
"I'm just thinking, 'How many days do we have?' and I mean, it's a blessing that we get to go through this with our children and our family and it's just something unique and rare," Brandy McCubbin told WDRB.
The calf was named Lucky by the McCubbins' five-year-old daughter, Henley, after her parents told her the rare animal was lucky to be alive. Most such genetic or developmental defects are aborted in the womb, although a few make it to birth. Most of those die within a few days.
For a two-faced or two-headed animal to make it to adulthood is extremely rare. It's considered ultrarare in the wild, although two-faced cat "Frank and Louie" lived to at least 12 years old, thanks to the care of its owners.
So far, Lucky has been doing well, the McCubbins said, although the middle two of her eyes don't work. She can only walk in circles and falls down a lot.
Lucky needs some help eating, and both mouths move at the same time.
When Stan first saw the calf, he thought he was seeing two animals lying close together. But then he was "blown away" by what he saw.
Developmental biologist Arkhat Abzhanov at Imperial College, London told the BBC that rare two-faced and two-headed animals develop in a few different ways. Sometimes, a single fertilized egg does not separate completely.
Other times, a gene that controls for head width gets overexpressed, and a head grows so large in the womb that it actually splits into two faces or heads.
"Those kind of mutants are rare, but they're reported in domestic animals and in the wild," Abzhanov told BBC.
The condition of having two faces is called diprosopus or craniofacial duplication.
The opposite affect can also occur, when a head gets so narrow that it collapses in on itself, producing a "cyclops."
Another possibility is that certain cells—called an organizer group–that trigger development of a head or face somehow get transported to another part of the body.
Whatever the exact cause, the McCubbins say they are committed to taking care of Lucky and making sure the calf is as comfortable as possible, for as long as possible.