“It’s a—it’s possible, or the—“What is purple and hums?” Of course, the answer is: “An electric grape.” Or: “[…] why does it hum?” “It doesn’t know the words.” And these jokes have no story line, they’re just conundrums. And the kids eat them up. They don’t.., they think the old story line jokes are for—strictly square.”

— Marshall McLuhan, see also “Address at Vision 65” , p. 1