While interviewing Jon Stewart on 'The Late Show' last night, David Letterman told the tale of why Oprah really hates him. Letterman explained that long before their 16-year feud, Letterman pulled a prank on Winfrey at a french restaurant that left a bad taste in her mouth. In what sounds like a scene out of a Larry David TV show, Letterman made her pay for his lunch without her knowing about it.