in the episode from season 2, "DISCO INFERNO" there's a mistake. It's set in April 1976, and in one scene Sam's watching an episode of "SATURDAY NIGHT LIVE". He's watching a sketch with Bill Murray and the Coneheads, then one with Chevy Chase. But, sine "SNL" started in Oct of 75; April 1976 would be its first season still. And both Bill Murray and the coneheads weren't on until the 2nd season. In fact Bill Murray replaced Chevy Chase.
But, I'm sure the series had a few historical errors.