Should I poop in a litterbox?
Why do you wanna poop in a litterbox?
I want to see how it feels to use litter box to understand my cat's perspective about it.
It's weird to use your pet's litter box as a toilet. Those are only for cats, you should use the bathroom.
what's wrong? My cat uses the litter box as a toy
There is never a good reason to ever need or want to use a cat's litterbox. Your curiosity is hopefully sated and you won't  need to do that again. Please use the proper bathroom next time and don't bother your cat's private spot.