As with many old TV programs, Carol Burnett’s long-running variety show (1967-1978) keeps finding its way onto DVD in new configurations. “Together Again” includes three complete episodes, prefaced by Burnett’s quick responses to audience questions. The first program is remarkable for a guest appearance by silent star Gloria Swanson, decades after doing Norma Desmond. The floating cast of visiting stars helped augment the comedic talent of regulars such as Harvey Korman and Vicki Lawrence.