Both Paul Simon the singer-songwriter and Paul Simon the senator and presidential candidate showed up for last weekend's edition of "Saturday Night Live," appearing in an impromptu spoof about their shared name. The two told the audience they did not know which of them was supposed to be this week's star: "It's a comedy show and it's a music show so it's got to be me," the musical Simon said, with the senatorial Simon responding, "Somebody should have told me sooner. I've been rehearsing since Thursday." The candidate's appearance resulted in some criticism Sunday on "This Week with David Brinkley." Simon said Gary Hart's return to the campaign was a "trivialization," and Sam Donaldson countered by saying Simon's "SNL" appearance could be considered in the same light. "You have to have a little exposure," Simon said, "and that was exposure."