On Sunday, for one night only, lights will go up on what may be the greatest concentration of comedy talent ever assembled for a live television event. It will broadcast from Midtown Manhattan at 30 Rockefeller Plaza’s Studio 8H, the home of Saturday Night Live since it first aired in 1975. NBC will celebrate SNL’s milestone fiftieth anniversary with a three-hour special, bringing together legends of the show’s star-making, culture-defining history, plus A-list friends of the show like Paul McCartney, Scarlett Johansson, Miley Cyrus, and Dave Chappelle. Tickets are unavailable at any price. Meanwhile, in Texas, a team of librarians is preparing a parallel unveiling of SNL memories that, while not quite as glamorous, will endure for generations and be available to the public at no cost. The Lorne Michaels archive, donated…