1. Do not tear this package.
2. Find the object. Break the small water-bag inside the package which will be full of air immediately. Drop the bag beside the object.
3. When the bag pop and air.
4. Eating prohibited.
The above being the instructions printed on the packaging of a mature and sophisticated "novelty" item, the Fart Bag ("BOOM"), which the boys brought home from a recent birthday party (thanks Lyn, thanks Rob).
Instruction 2 takes on added significance when the user realises that he has no idea what is the "object" referred to. I can read instruction 3 over and over with no diminution of pleasure. When the bag pop and air. That about says it all, really.