The reason I came up with myself to explain to my children how corn, although fully chewed, still comes back out whole during a bowel movement.
Based off of the story of the poor cobbler and his wife who could not afford to make shoes to sell so that they could buy food (but were rescued by elves in the night who made the shoes for them to sell), Butt Elves work the same way, living inside your butt and stitching the corn back together. This explains the strange phenomena that most parents just can't explain to their youngsters.
"Daddy - why does my corn come back out whole in my poop when I chewed it up?"
"Well, sweetie, the butt elves must have been working overtime again!"