Cheshire cat

Having a perpetual, mischievous grin, one that is often indistinguishable from smugness. Although the Cheshire cat is best known as a character in Lewis Carroll's Alice's Adventures in Wonderland, it appeared much earlier in popular English culture, so the phrase may have originally referred to cheese made in the country of Cheshire and molded roughly to resemble a grinning cat. Lewis Carroll's feline had the ability to disappear until only its smile remained. The cheese variety would be sliced from hind end to front, which similarly gave the impression that its smile—if cheese showed emotion—would be the last to go.