A little boy asks his dad, "Where does Poo come from?". His father is taken back by the question but decides to give he son the facts straight up.
"Well, son," he says, "food passes down the esophagus by peristalsis. It enters the stomach, where digestive enzymes induce a probiotic reaction in the alimentary canal. This extracts the protein before the waste products enters the colon. Water is absorbed, whereupon it enters the rectum finally to emerge as poo."
"Wow," says the boy. "So where does Tigger come from?"