Pioneer PBS FOO 67TH MYS JON STEWART: MARK TWAIN PRIZE TUESDAY, JUNE 21 AT 8 P.M. The Kennedy Center MARK TWAIN PRIZE FOR AMERICAN HUMOR Pioneer PBS FOO 67TH MYS JON STEWART : MARK TWAIN PRIZE TUESDAY , JUNE 21 AT 8 P.M. The Kennedy Center MARK TWAIN PRIZE FOR AMERICAN HUMOR