The cat's ass
The look of surprise and shame was unmistakeable on Kitty's face as his head popped up next to his foot. My parents and I had been sitting in the backyard when my mom pointed out that Kitty's foot was waving alone over a window sill. His head popped up next to his foot and the look on his face caused us all to laugh, having instantly understood how he felt.
I've heard before that animals don't actually possess the necessary muscles to make complex facial expressions. I don't completely believe this, but perhaps it's that cats have just enough of the required facial expressions to show shame, surprise, and disgust simultaneously.
That's right, Kitty is a boy cat.