The wolf.

Born into a world dark and cold. Raised to show no fang or claw. The wolf joined the pack, trained to use the fangs and claws long sealed away. But the wolf was pushed aside, left by the pack. Told to live on its own, to wear the clothes of a man. No matter how much the wolf tried, it could not fit so it gnawed and it gashed at itself; but to no avail. But then it realized: A wolf in man's clothing is still a wolf.  

A wolf is a wolf until it dies, it can be nothing else.