Cheshire Cat from Alice's Adventures in Wonderland book.
One of the most known adaptation was in 1951, Disney animated film Alice in Wonderland. Cheshire Cat is an intelligent yet mischievous character that sometimes helps Alice but sometimes gets her into trouble.
My favorite portray of Cheshire Cat (voiced by Stephen Fry) is by Walt Disney movie Alice in Wonderland (2010), directed by Tim Burton. I love his big eyes, wicked smile, intelligence but yet coocoo weirdness (in a good way). And he looks so fluffy.
“Only a few find the way, some don't recognize it when they do - some... don't ever want to.”
“We're all mad here.”
Video where Alice meets the Cheshire Cat.