An extra-toes cat isn't a breed. It's any cat born with polydactyly, a harmless genetic variation that adds toes 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 a litter. It's especially common in New England and Atlantic Canada, where big-pawed ship cats were prized as mousers.
The "Hemingway" nickname comes from Ernest Hemingway, who was given a six-toed cat named Snow White. Most extra-toed cats are domestic shorthairs or longhairs, and their personalities vary as much as any cat's. Weight usually runs 6 to 15 pounds, and many live 12 to 18 years. The main care difference is nail trimming, since extra claws can curl into the paw pads.