Answer:
When it was young, it had a tail. When it grew up, it had knees
I'm known for being stubborn and saying 'hee-haw.' What am I?
Long slim and slender. Dark as homemade thunder. Keen eyes and peaked nose. Scares the Devil wherever it goes.
What jumps when it walks and sits when it stands?
I have eight to spare and am covered with hair.
Who makes it, has no need of it. Who buys it, has no use for it. Who uses it, can't see it. What is it?