Revealing mistake: Samuel Clemens (Mark Twain) spends a night in North Fork while the wheel of a stagecoach he is riding in is being repaired. Clemens is fishing at a lake and Mark McCain says, "You've caught a fish " Clemens tells the boy to reel in the fish. The boy jerks the rod and pulls the fish out of the water. The fish is obviously a fake which a stagehand had attached to the hook. The fish is motionless and is not even wet.
Revealing mistake: Two former Civil War officers prepare to make camp in a sandy area surrounded by large rock formations. It is obvious that they are on an indoor set. As one man takes a few steps, the sound of his boots hitting the wooden platform beneath the sand can be heard.
Strange Town - S3-E5
Revealing mistake: After Micah is badly beaten, he's leaning on a barbed wire fence. The camera pushes in from behind him as the wire grows closer to the camera. Someone off-screen pulls it down out of the shot.
Closer Than a Brother - S3-E22
Revealing mistake: In the saloon, Micah announces he is resigning as sheriff. He sets two bottles of liquor on the bar and Lucas McCain immediately slaps them away. The bottles are obviously not real because they shatter into hundreds of pieces as soon as Lucas touches them.