An extra-toes cat isn't a breed. It's any cat born with polydactyly, a harmless genetic variation that adds digits to one or more paws. A typical cat has 18 toes, while polydactyls often have six or seven on a front paw, sometimes forming a mitten-like thumb. The trait is dominant, so one affected parent can pass it to roughly half of a litter.
The Hemingway nickname comes from writer Ernest Hemingway, who was given a six-toed cat named Snow White. Most extra-toed cats are domestic shorthairs or longhairs, so coats, sizes and personalities vary as much as in any cat. Expect a medium-sized cat of about 6 to 15 pounds with moderate shedding. The main care difference is nail trimming, since extra claws can curl into the paw pads.