Starring: Robert Conrad, Dick Cangey, Ross Martin, Whitey Hughes
The Night of the Circus of Death - S3-E9
Continuity mistake: The draperies are fully engulfed in flames when the murderer runs through them and out onto the balcony. Cut to an exterior shot as he escapes, and the window dressings are perfectly intact with no sign of the fire. (00:03:10)
The Night of the Avaricious Actuary - S4-E11
Continuity mistake: The letter from the Cyclops Insurance Company that Gordon pulls out of his pocket is folded, wrinkled, and well-worn. In the close up of the same letter West reads, the letter is white, pristine, and not wrinkled or folded.
The Night Dr. Loveless Died - S3-E4
Trivia: Dr. Loveless' uncle's name, "Liebknicht", is, aside from the addition of the letter "k", German for "Loveless".