It seems to me that the idea of parody is part of the human psyche. Whenever something gets too familiar or plays too long on our emotions humans tend to parody it. The "Lord Of Misrule" comes to mind, as does the role of the Fool in medieval courts. JibJab pokes fun at Bush, "Macbird" satirized LBJ and you can find many other examples, both current and historical. To cite but one set of examples, both the Union and the Confederacy parodied each other's songs during the American Civil War. And I've seen some parodies of "The Ballad of the Green Berets" that...heck, some of them are in the DT.