the Cheshire Cat, Lewis Carroll

"We're all mad here," said the Cheshire Cat.

"I'm mad. You're mad."

"How do you know I'm mad?" ,said Alice.

"You must be," said the Cat, "or you wouldn't have come here."

"And how do you know that you're mad?" asked Alice.

"To begin with," said the Cat, "a dog's not mad. You grant that?"

"I suppose so," said Alice.

"Well, then," the Cat went on, "you see, a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."

Upon these words, the Cheshire cat vanished slowly, beginning with the end of the tail, and ending with a grin, which remained some time after the rest of it had gone.

"Well! I've often seen a cat without a grin," thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in my life!"

Lewis Carroll, Alice's Adventures in Wonderland (1865)