The world lost a comedy legend this week with the passing of Don Rickles, one of the funniest (and meanest) voices ever to take the stage. Newspapers across the country have done their best to memorialize this larger-than-life entertainer, but we think that should be left to someone who knew him best: Frank Sinatra.The singer first met Rickles in 1957 and they stayed lifelong friends afterwards. Rickles was famously the only person allowed to joke about Sinatra's fragile ego, and as you can tell from this story he took his job seriously.Throughout their careers these two icons often