Every Tamagotchi makes a poop, at least trice a day. In the old Tamagotchi versions, Tamagotchis made up to 10 poops a day. To clean the poop, you must select the Toilet Command (The Toilet Command is the third command in most Tamagotchis). If you don’t clean the poop, the Tamagotchi can become sick, or even die.
-Tamagotchi Wiki