Plot: Bill Cosby receives the Mark Twain Prize for American Humor. The ceremony features clips from his classic shows and tributes from former "Cosby Show" cast mates Phylicia Rashad and Malcom Jamal-Warner, as well as Carl Reiner, Chris Rock, Jerry Seinfeld, Danny Glover, Dick Gregory, Wynton Marsalis, Rita Moreno, Willie Nelson, Sinbad, Len Chandler, James dePriest and Jimmy Heath