The Cheshire Cat is a fictional cat popularized by Lewis Carroll’s depiction of it in Alice’s Adventures in Wonderland. Known for his distinctive mischievous grin, the Cheshire Cat has had a notable impact on popular culture.

Alice first encounters it at the Duchess’s house in her kitchen, and then later outside on the branches of a tree, where it appears and disappears at will, engaging Alice in amusing but sometimes vexing conversation. The cat sometimes raises philosophical points that annoy or baffle Alice. It does, however, appear to cheer her up when it turns up suddenly at the Queen of Hearts’ croquet field, and when sentenced to death baffles everyone by having made its head appear without its body, sparking a massive argument between the executioner and the King and Queen of Hearts about whether something that does not have a body can indeed be beheaded.

At one point, the cat disappears gradually until nothing is left but its grin, prompting Alice to remark that she has often seen a cat without a grin but never a grin without a cat.
From Wikipedia