Starring: Robert Conrad, Dick Cangey, Ross Martin, Whitey Hughes
The Night of the Kraken - S4-E6
Factual error: West and Artie are trying to move a cabinet from the wall. A closeup shot shows West's left hand entering from the right side of the shot to press a button that allows a secret panel to open. Unless West twisted his left hand 180°, then him pressing the button as shown is not possible.
The Night of the Bubbling Death - S3-E1
Revealing mistake: As West drags the body of a bad guy out of the scene, the supposedly unconscious man is holding his head up so as not to have his head dragged through the dirt. A truly unconscious person's head would flop back on to the ground.
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".