As the first documentary about legendary comedian Joan Rivers since her death, ‘Joan Rivers: Exit Laughing” will debut April 1 at 10 p.m on New York’s PBS WNET Thirteen and will feature Sarah Silverman, Whitney Cummings, Kathy Griffin, Dick Cavett, Don Rickles, Lily Tomlin, Marlo Thomas and many others. It will be the first in a planned series documentary films about comedic titans and it will show how Joan “revolutionized the field as a pioneer to forge a path for the wave of female standups in the 1970’s and 1980’s and beyond,” according Jeffrey Pancer, Head Curator of the Comedy Hall of Fame.