When I got home from school I asked if I could have a funnel and a glass of water and a penny. Then I told Christopher how to play a game.
The rules are:
you stick a funnel in your trousers,
you balance a penny on your chin,
and try to make it drop into the funnel.
When he leaned back to put the penny on his chin I poured the glass of water down the funnel and it looked like he had wet himself.