An guy, who had spent his whole life in the desert, goes to visit a friend who had moved to town. He'd never seen a train or the tracks they run on.
While standing in the middle of the railroad tracks one day, he hears this whistle -- Whooee da Whoee! -- but doesn't know what it is. BAM!!, he's hit by the train and tossed to the side of the tracks. It was only a glancing blow, so he was lucky enough to live through it with a few broken bones and some bruises.
After weeks in the hospital recovering, he's at his friend's house attending a party one evening. While in the kitchen, he suddenly hears the teapot whistling. He grabs a baseball bat from the nearby closet and proceeds to batter and bash the teapot into an unrecognizable lump of metal. His friend, hearing the noise, rushes into the kitchen, sees what's happened and asks the guy, "Why'd you bust up my teapot?" The desert man replies, "You gotta kill these things when they're small."