why does your cat grin like that?

"Please, would you tell me," said Alice, a little timidly,
"why your cat grins like that?"
"It's a Cheshire cat," said the Duchess,
"and that's why."
-- From Lewis Carroll's 1865 novel, Alice's Adventures in Wonderland

While stopping to take a picture to submit to the Tucson Mural Project I spotted the above cat reflecting off a window. I didn't have time to watch it vanish as the sun went down...

Here's a link to the actual mural.