Answer:
My keepers feed me colored balls. With sticks they store on my den walls. Sometimes I store them in my pouch. Sometimes deep in my belly; ouch!
I am tomorrow's yesterday and yesterday's tomorrow. What am I?
Weight in my belly, trees on my back, nails in my ribs, feet I do lack. What am I?
I am the tool for inspiring many. Buy me in the store for not much more than a penny. Don't overuse me, or my usefulness will go. What am I?
What do people spend a lot of money on every year, but never want to use?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.