Abstract: Why did the Beatles become a worldwide sensation? Why do some cultural products succeed, and others fail? On one view, the simplest and most general explanation is best, and it points to quality, appropriately measured: the Beatles succeeded because of the sheer quality of their music. On another view, timely enthusiasm or timely indifference can make the difference for all, including the Beatles, and informational cascades are often necessary for spectacular success. For those who emphasize informational cascades, success and failure are not inevitable; they depend on seemingly small or serendipitous factors. There is no question that the success of the Beatles, and the rise of Beatlemania, involved an informational cascade. We may doubt that in a counterfactual world there might have been Kinksmania or Holliesmania, but it would be reckless to rule out the possibility that some other band, obscure or unknown, might have taken the place of the Beatles.