Answer:
It's anything but amusing when this body part gets hit.
Bold are the first; true are the second; playful are the third; clever are the fourth; forceful are the fifth.
A time when they're green. A time when they're brown. But both of these times, cause me to frown. But just in between, for a very short while. They're perfect and yellow. And cause me to smile.
Only two backbones and thousands of ribs.
Always wax, yet always wane: I melt, succumbed to the flame. Lighting darkness, with fate unblest, I soon devolve to shapeless mess.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?