A boy with a pea shooter, ran out of ammunition, and discovering a box of laxative pills, tried one in his blow gun.  To his great joy, it fit. 

There was a boarding house near by, and every Wednesday noon a big pan of custard was placed upon the window sill to cool.  From his vantage ground in the window of another house, the boy shot all the pills into the custard. 

The boy soon found out that he was an expert marksman and the Wednesday custards became history.