When Mason and Mia were babies, they pooped a lot - always in their diapers. Now that they're big kids, it's time to use the potty. But what is the potty for? Naps? NO. Books? NO. Playing the drums? No, no, no! Mason and Mia look ahead to official big-kid territory in this hilarious, instructive story that follows in the tradition of Once Upon a Potty - but with special emphasis on that momentous toddler milestone: pooping in the potty!