Look at those big feet! This is a polydactyl cat, born with more than the regulation number of toes. Polydactylism can affect any animal with toes, but the genetic anomaly is relatively common in domestic cats, which normally have five toes on the front paws and four toes on their back paws. Photograph by Flickr user Actor212.
Polydactylism (literally "many-fingered") is a genetic mutation that is passed down via a dominant gene. The trait is found most often in western England, Wales, and the eastern parts of the United States and Canada. They are historically sought out as ship's cats, which explains their prevalence on "both sides of the pond." We don't know which side they originated on. However, the mutation can arise spontaneously in any cat population, so all polydactyls are not necessarily related to each other.
The condition is usually benign, and cats rarely suffer from having extra toes in and of itself. There is a genetic condition called feline radial hypoplasia in which extra toes are common. Radial hypoplasia causes other birth defects in addition to polydactly, such as underdeveloped or twisted forelegs, which is a genuine disability, and such cats should be neutered to prevent passing on the abnormality. But those cases are in the minority.
Unlike most mutations, extra toes don't hinder a cat, and can be considered an asset. Just the appearance of polydacts causes cat lovers to fall for them.
Polydacts were popularized by author (and cat lover) Ernest Hemingway, who was given a six-toed cat by a sea captain named Stanley Dexter in the 1930s. Hemingway loved the cat he named Snowball. About 60 cats still live at the Hemingway Estate in Key West, where they are fed and protected as a historical treasure. About half are polydacts, possibly the decendents of Hemingway's cat.
Another famous polydactyl was a cat owned by President Theodore Roosevelt named Slippers. See a picture of Slippers. The Roosevelts had a veritable zoo in the White House, and Slippers was not the only cat.
Some polydactyl cats present "mitten paws," which occurs when the extra toes are attached on the medial side, or "thumb" side of the paw. This can lead to a cat that appears to have opposable thumbs. Some cats have learned to manipulate the extra digits like a human thumb. Cats have been known to use this ability to pull stunts that amaze their owners, such as opening latches and windows. I haven't found any case of a polydactyl cat successfully using a can opener, but there's always a first time. You know they are working on it!
Cats that have multiple toes that aren't "mitten paws" just appear to have big feet, which are called "snowshoe paws" or "pancake feet." They might remind you of the Canada lynx, which normally has extra large paws (even without extra toes) which enables them to travel on top of snow.
The Guiness World Record for the number of toes on one cat is 28 toes. Jake, a cat owned by Paul and Michelle Contant of Ontario, Canada, was crowned the record holder in 2002. However, a kitten born in 2011 named Fred also has 28 toes and may be a contender. Fred's littermate Ned has 26 toes.
Milo has seven toes on each front paw. He gets around just fine on those big feet!