The ba dum tss comes from live comedy, where a stage drummer would punctuate a joke with a quick rimshot and cymbal crash, a trick carried over from vaudeville and variety shows into stand-up clubs, radio and television comedy. Because the sound instantly signals that a joke has just landed, or deliberately failed, it became a shorthand for bad puns in cartoons, sitcoms and later online videos. It remains popular as a dramatic sting in its own right, a tiny piece of musical timing that needs no explanation.