Top 10 questions about Letterman's beloved Top Ten

David Letterman's Top Ten debuted in 1985 as a parody of the types of lists popular in women's magazines. It went on to become a cultural institution, spanning some four decades over two networks. The list, delivered nightly in reverse order with a little drumroll, included memorable zingers about politicians, celebrities, and current events. On the eve of Letterman's retirement, we test your knowledge of the hallowed list of all lists.