"Top Billing" is my favorite episode of the series, and has all the elements: creepy, a great storyline, and a great ensemble cast that deliver excellent performances. Jon Lovitz is perfect as the idealistic, unlovable loser actor with a face better suited for radio. Bruce Boxleitner is great as the arrogant "face" actor with a disdain for the artier side of the craft. Paul Benedict (Mr. Bentley from the 'Jeffersons') cranks up the creep factor as the director's assistant, but the best performance comes from zany John Astin. His over-the-top portrayal of director Nelson Halliwell is absolutely brilliant.
The pacing is great, the shocks have impact despite a minimum of violence, and the plot twist is a great one. Each cast member, no matter how brief the part is, turns in an inspired performance, adding to the quality of the episode. The bad day Lovitz suffers through is a great setup for his final audition. The rivalry between Barry and Winton creates great tension, and the whacked-out theater troupe is the icing on the cake.