is it a shooter marble or a normal marble? am i just making up that there are 2 diff sizes? eh, probably marble. i'd never crap the same if a softball came out.
Sadly, I'll have to go with softball; the little passage through which the marble would have to travel is not meant for anything with a measurable diameter.
I had a four month ordeal with a jagged 5mm kidney stone. It didn't want to pass from my ureter tube to the bladder and ended up needing some shock treatment. A marble ain't passing through