Peter Gallagher and On the Twentieth Century each made their Broadway debuts during the same 1977 to ’78 season. Since then, the musical has rarely been seen, but the actor has had one of those rare careers in which he’s perpetually popped up in most every performance medium and genre without wearing out his welcome or curdling into type. On Broadway, he’s run the gamut from Hair, in which he made that debut in the love-rock musical’s short-lived first revival, to the tragic Long Day’s Journey Into Night with Jack Lemmon and Kevin Spacey, to the golden-age musical Guys and Dolls with Nathan Lane. He’s played key roles, usually as a slickster, in films that helped define their times, like Sex, Lies, and Videotape and The Player. On television, Gallagher has matured into authority figures—mostly trustworthy, sometimes not—on such series as The O.C. and Togetherness. He’s even put out an album, 7 Days in Memphis, and toured the country with a cabaret act peppered, like his conversation, with spot-on impersonations of the many legends he’s known.