An extra-toes cat isn't a breed but a trait. Polydactyly is a harmless genetic variation that gives a cat extra digits on one or more paws, often a mitten-like thumb on the front feet. It's especially common along the East Coast, where sailors prized big-pawed mousers, and it can be passed on by a single affected parent.
The Hemingway nickname comes from Ernest Hemingway's six-toed cat, Snow White. Most extra-toed cats are domestic shorthairs or longhairs, so coats and personalities are as varied as any cat's. In Allentown that could mean a sleek short-coated tabby or a fluffy longhair who needs regular brushing. The main care difference is claw trimming, since extra nails can curl into the paw pads.