An extra-toes cat isn't a breed but 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, and it's especially common in New England, where ship cats with big paws were prized as mousers.
The 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 are as varied as any cat's. The main care difference is nail trimming, since extra claws can curl into the paw pads, so a steady trim routine matters more than the toe count.