Showdown with Rance McGrew - S3-E20
Continuity mistake: Rance McGrew's white horse is tied up with its head just a few inches from the hitching rail, but a moment later is untied and several feet away from the rail. Next shot, it's tied up close again, though no one's touched it. Finally, it's completely loose, and at the episode's end, is wandering into the street. (00:22:00 - 00:23:30)
Showdown with Rance McGrew - S3-E20
Continuity mistake: The saloon's windows are much narrower inside than they are on the outside. (00:17:20)
Continuity mistake: The events shown are supposed to take place at almost exactly midnight, yet when Conny goes to the graveyard the sky is bright and everything is well lit, much brighter than moonlight. Just as he enters the graveyard there is an abrupt change in lighting and the scene is suddenly much darker.
Showdown with Rance McGrew - S3-E20
Continuity mistake: The car Rance drives onto the set can be seen in the street from inside the saloon, but disappears when Rance, in character, comes through the swinging doors. It's visible again in the very next shot, but vanishes anew when Jesse James comes through the doors, after which it yet again reappears in the very next shot. (00:04:30 - 00:07:20)
Continuity mistake: During the birthday party scene, as the close-ups and master shot are intercut, Anthony's hair changes back and forth from being combed straight forward to parted on the left and combed to the side. (00:15:10)
The Jungle - S3-E12
Continuity mistake: Richards opens the door and finds a lion on the bed over his wife's body. When the door first opens, the corpse has dark hair and the blanket is twisted and disarrayed. But when the shot cuts to the lion leaping, the corpse's hair is a lighter color and the blanket is neatly spread across the bed. (00:23:40)
Continuity mistake: When the Union soldier arrives on the horse, Lavinia points a shotgun at him, holding it at chest level. But when the shot cuts, she suddenly has it up to her cheek. (00:15:00)
Continuity mistake: The hundreds of ropes used by the tiny people to pull down Craig's statue vanish in the next shot, when the statue hits the ground. (00:23:55)
Continuity mistake: When Fats makes his shot to set up the last ball for Jesse, the cue ball stops on the bumper side of the dot. When Jesse goes to take the shot, the cue ball is closer to the side pocket he's leaning over.
Continuity mistake: Block 6 looks to have a no cardboard over the window beside the "Block 6" sign. Then later on they have cardboard there. (00:12:20 - 00:14:55)
Continuity mistake: The Block 6 door is closed all throughout the video, then when Captain runs towards the door it's opened. (00:07:55 - 00:14:55)
Continuity mistake: Becker is standing on the porch at "Block 6" and there are no handrails. When we return to Becker he is in the center of the square area and in the background handrails are there. (00:07:55)
Continuity mistake: The captain goes to "Block 6" which we see is the 1st floor with stairs which are in line with the porch, but when he leaves the stairs go off at a 90 degree angle from the porch. (00:04:50 - 00:06:20)
The Last Rites of Jeff Myrtlebank - S3-E23
Continuity mistake: An entire piece of toast disappears off of Pa's plate from one shot to the next. (00:08:40)
The Last Rites of Jeff Myrtlebank - S3-E23
Continuity mistake: Jeff corners Orgram behind a tree with a tire swing hanging from it and punches him to the ground. But in the next shot, Orgram is still on the ground and the tree and tire swing are nowhere in sight. (00:17:35)
Continuity mistake: When we first see it, the grandfather clock is stopped at 2:33. But when Alex opens the case to adjust and restart it, the clock reads 4:40, and he moves the hands to 2:33 after checking his watch. (00:01:05 - 00:03:50)
I Sing the Body Electric - S3-E35
Continuity mistake: When Tom races into the house, the exterior shot is of a front door with six window panels. But when we cut to the interior view of him coming inside, the door has suddenly become solid, with no windows at all. (00:13:20)
Continuity mistake: When the decrepit Mr. Holt gets his new young body (briefly necessitating a different actor in the role), his German accent mysteriously disappears. He gets it back when he returns to his old body. (00:21:00)
Continuity mistake: During Rod Serling's opening narration you can see over his shoulder part of the outline of the portal to the 4th dimension, which would be drawn there later in the story.
Continuity mistake: After sounding the "alert" for his guests, Raden turns around to fully face them, and as he addresses the Reverend, from the back his hand is gripping the arm of the chair. In the the next moment, there is a frontal shot, and Raden's hands are folded on his lap.
Answer: It's explained in the episode. The aliens are experimenting to see how humans react to various scenarios. This just happens to involve them using super strength.
Thanks. It's been a long time since I saw the episode so I forgot.