The Night of the Camera - S4-E10
Revealing mistake: As Bosley Cranston fights the bad guy, Pat Paulsen's stunt double does not look like Paulsen - the stunt double is much younger looking.
The Wild Wild West (1965)
1 revealing mistake in The Night of the Camera - chronological order
Starring: Robert Conrad, Dick Cangey, Ross Martin, Whitey Hughes
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.
Trivia: Due to the rigorous stunts he performed, actor Robert Conrad would often rip out the seat of his already too tight pants.