Tonight’s vintage episode of Saturday Night Live is from 1979, the final season featuring most of the original cast members. In 1972, Rick Nelson wrote and sang “Garden Party,” a hit about how weary he was of being asked to sing only his old songs. Seven years later, the former heartthrob star of Adventures of Ozzie and Harriet showed up on Saturday Night Live – not as musical guest (that was Judy Collins), but as guest host. Yet even as guest host, he finds time to sing such songs as “Hello Mary Lou” and “Travelin’ Man,” and to play in a Twilight Zone sketch in which he finds himself trapped in a series of 1950s sitcoms.