The Night of the Egyptian Queen - S4-E8
Continuity mistake: The first shot of West's eyes, after the opening credits, shows them to be a bit different than usual - as if they had an allergic reaction to something. The second, third, and fourth shots show the eyes back to normal, but the shot of him walking the princess to the door shows a very puffy faced West. After walking her to the door when he turns around, West is back to looking like his typical self for the rest of this episode.
The Night of Fire and Brimstone - S4-E9
Visible crew/equipment: The camera's shadow is visible on the wall map as Captain Butler speaks with West.
The Night of Fire and Brimstone - S4-E9
Factual error: West fires seven rounds from his six-shooter without reloading to cover Gordon's escape.
The Night of Fire and Brimstone - S4-E9
Continuity mistake: After West shoots the mine wall with the grappling arrow, the line connected to the arrow is taut. The quick shot back to West shows the line loose with lots of slack, then cuts back to the arrow and the line is taut.
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 Night of the Camera - S4-E10
Continuity mistake: When West finds the half poker chip, he moves to place it in his left outside vest pocket with his left hand, but the next shot shows him placing the chip into the inside left pocket of the vest with his right hand.
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 of Miguelito's Revenge - S4-E12
Continuity mistake: When West and Pike pour a drink for "absent friend" Arte, the glass is placed between a newspaper and a silver dish. In the following close-up, the paper and dish have disappeared and the glass sits alone on the table. (00:49:50)
The Night of Miguelito's Revenge - S4-E12
Revealing mistake: An obvious dummy floats out of the underwater coffin after West pops open the top of the coffin.
The Night of Miguelito's Revenge - S4-E12
Other mistake: The sandbag that almost falls on Pike and West splits wide open upon impact with the floor, but subsequent shots of the bag show it almost intact.
The Night of Miguelito's Revenge - S4-E12
Continuity mistake: The barber chair West sits in has dark wood arm rests, yet the close up of his hand as he is being chloroformed by Loveless shows white arm rests.
The Night of Miguelito's Revenge - S4-E12
Continuity mistake: As Jeremy Pike holds the glass of brandy, it changes position from being up to down, then up again.
The Night of Miguelito's Revenge - S4-E12
Revealing mistake: At the beginning of the episode, as Jim West walks away from the newsstand vendor and closes the magazine, a 1967 ad for DieHard batteries ("The DieHard Fights the Common Cold") can be seen on the right-hand page of the prop magazine, in a modern sans serif font.
The Night of Miguelito's Revenge - S4-E12
Continuity mistake: In the scene before the third freeze frame, a large coffin-like rectangular object slides into the water. West is inside this structure. All sides are completely flat. We see the object under water sinking. This one is much shorter, has an oval window, and the side is not completely flat when compared to the one that enters the water. After the freeze frame, West is sitting up with his legs completely extended. The dimensions of this under water container would have to have height and width much longer than the other two containers that have been shown.
The Night of Miguelito's Revenge - S4-E12
Visible crew/equipment: The wire suspending Pike's flying butterfly bomb is visible as it flies around the circus tent.
The Night of Miguelito's Revenge - S4-E12
Revealing mistake: Dr. Loveless' body flies out of the cannon before the cannon's blast propels him out the barrel.
The Night of Miguelito's Revenge - S4-E12
Revealing mistake: Stock footage of West and Gordon's train show it on a siding with no green foliage near it, but when West enters his private car, green bushes are seen very close to the train through the train car's open door.
The Night of Miguelito's Revenge - S4-E12
Continuity mistake: Loveless' goon holds his gun at a high angle to Pike's head, but the next shot shows the gun at a much lower angle.
The Night of Miguelito's Revenge - S4-E12
Continuity mistake: The pencil on Barlow's desk disappears in the view over Barlow's right shoulder, then appears when seen over Pike's left shoulder as the scene switches back and forth.
The Night of Miguelito's Revenge - S4-E12
Character mistake: The store window's sign says, "Denver Mercatile" rather than "Mercantile."