malformalady:

A polydactyl cat is a cat with a congenital physical anomaly called polydactyly (or polydactylism, also known as hyperdactyly), that causes the cat to be born with more than the usual number of toes on one or more of its paws. Regular cats have five toes
on their front feet and four on their back, for a total of 18. But
polydactyl [pronounced pol-ee-dak-til] cats boast more toes, usually on
their front feet. Polydactyl cats are known by many names, including “Hemingway cats,” “mitten cats,” “big-foot cats” and “six-toed cats” — or even “cats with
thumbs.”