After being on the air for more than three decades, the essential format of this show hasn't changed: Get an A-list guest host (or reasonable facsimile) and throw him or her into sketches with the ensemble players, which have included such heavy hitters as Will Ferrell, Jimmy Fallon, Tina Fey, Jane Curtin, Chevy Chase, Bill Murray and Mike Myers. Each week's show also offers two musical numbers from someone at, or aspiring to, the top of the charts.