Where does poo come from?

Courtesy of me sis':

A little boy asks his dad: 'Where does poo come from?'

His dad explains that food passes down the oesophagus to the stomach, where digestive enzymes induce a probiotic reaction in the alimentary canal; this reaction extracts protein before waste products descend via the colon and rectum to emerge as 'poo'.

Blimey, says the little boy -

'And what about Tigger?'

Well, we think it's funny . . .