In comedy, few are as influential - and elusive - as Jim Downey. During his 30-year tenure as a writer on "Saturday Night Live," he penned era-defining sketches like Chris Farley's "Chippendales Audition" and defined the show's political satire with Dana Carvey's George H.W. Bush ("na ga da it") and Will Ferrell's W. Bush ("strategery"). [...]