When you have Anal sex ("forgetting" a condom, of course) and are finished, there is going to be an amount of
poo packed into your cock nostril. Afterwards, when you goto the bathroom, the pressure in the urethra forces the poo out in
banana shape. Placing a small quippit sieve in the toilet will allow you to collect these mysterious treasures.
Legend has it, if you collect 10 of these and bury them in the garden, you will be rewarded with 10 years of good luck.