BURBANK, CA - AUGUST 03: Comedian Norm Macdonald on stage at the 'Comedy Central Roast Of Bob Saget' on the Warner Brothers Lot on August 3, 2008 in Burbank, California. (Photo by Alberto E. Rodriguez/Getty Images for Comedy Central)

In the alternately hilarious and heartbreaking story, posted on Twitter, the comedian remembers his first encounter with "the funniest man in the world," who comforted a young Macdonald as he nervously sat in a dressing room prior to his first stand-up appearance on "The Late Show with David Letterman."