Answer:
What is pronounced like one letter, written with three letters. And belongs to all animals?
It's anything but amusing when this body part gets hit.
Who works when he plays and plays when he works?
What is the thing that stays the same size, but the more it's used the more it decreases?
Only one color, but not one size. Stuck at the bottom, yet easily flies. Present in sun, but not in rain. Doing no harm, and feeling no pain.
Iām grown from darkness but shine with a pale light. Very round I am and always a lady's delight.