Revealing mistake: When the main character proclaims, ".the new Walter Bedeker!" you can see the frames are running back and forth. You can tell by looking at the window curtains behind him.
Revealing mistake: When Hall races toward the window to jump, the stunt man is just a little too apparent as he leaps, primarily due to a very bad wig. (00:22:40)
Revealing mistake: When Lanser goes below deck frantically trying to find people and tell them to leave the ship, when he opens the door at end of the corridor, it's a bit too obvious that the hallway behind that door is nothing more then just a painting.
Revealing mistake: When Lanser drops the cup, you can quite see that he is drinking from an empty cup, since the steward never poured him any and yet he manages to get some of it on his suit.
And When the Sky Was Opened - S1-E11
Revealing mistake: After his flashbacks in his hospital room, Forbes looks at himself in The Mirror and he cannot see his reflection. But you can still see his arm in mirror.
Revealing mistake: In scene just after Rod Serling's opening narration, you can quite see that scene is being played in reverse because smoke is coming downwards back into the man's cigarette.
The Four of Us are Dying - S1-E13
Revealing mistake: As the men walk out of the alley, the block continues ahead of them. You can see it's a painted background.
I Shot an Arrow into the Air - S1-E15
Revealing mistake: Right after their friend dies and the commander talks about going into the mountains to search for any life signs, you can very briefly see Corry looking straight into the camera.
Revealing mistake: When Franklin leaves the check cashing window and walks to the right, a man with a pompadour haircut walks off screen left. In the next shot, with no time lapse, Franklin returns to his slot machine, and the same extra passes behind him from the right, once again exiting left. No way he could have moved that fast in the time allotted. (00:13:05)
Revealing mistake: Throughout the episode, the "frozen" people can be seen breathing and moving slightly. This is particularly apparent in the beauty contest tableau.
Revealing mistake: As Peter goes to the fishers, the pair shown on the bridge behind him are obviously photographs.
A Nice Place to Visit - S1-E28
Revealing mistake: When Valentine tries to shoot Pip, he shoots the lamp to see if his gun works. The lamp breaks a full second after he shoots it. It was obviously done by special effects.
A Nice Place to Visit - S1-E28
Revealing mistake: When Rocky evicts three women from the room and slams the door behind them, you can quite clearly see the entire wall shaking.
A Nice Place to Visit - S1-E28
Revealing mistake: After Valentine finds out he isn't in Heaven, he tries frantically to open the door. As he does, you can see the whole wall and door frame moving along with the door, showing that it's fake.
Revealing mistake: When "Selden" falls down the stairs it is obvious that it's a stunt double.
A Passage for Trumpet - S1-E32
Revealing mistake: Joey cannot see himself reflected in The Mirror. However when he walks past the booth, he has a clear reflection.
Revealing mistake: When all of the neighborhood children push Bevis's car for him, one of them looks directly into the camera.
Revealing mistake: One of the actresses who is supposed to be playing a mannequin doesn't start to smile until the camera is on her.
Revealing mistake: Mr. & Mrs. Castle wish for a million dollars in 5 and 10 dollar bills. But the bills they receive all have the same pattern printed on both sides, a pattern which which doesn't resemble any real US currency. There's also not nearly enough of the bills to total a million dollars. (00:12:30)
Nervous Man in a Four Dollar Room - S2-E3
Revealing mistake: The main character's reflection in a mirror has come to life and much of the episode is a confrontation between the character and his reflection. Although they made an effort to reverse the image (the reflection wears his watch on the opposite hand and he bites his fingernails with the opposite hand) they forgot to reverse the buttons on his shirt.
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.