A Thing About Machines - S2-E4
Revealing mistake: When the electric razor is coming down the stairs after Finchley, the wire used to pull it is visible. (00:19:50)
A Thing About Machines - S2-E4
Revealing mistake: When Finchley smashes the TV, the screen image stays visible for a short time after the screen is broken, revealing that the screen's image was superimposed.
A Thing About Machines - S2-E4
Revealing mistake: When the car is approaching the pool to push the man into the water, the tires tracks are visible in the grass, showing that the car had already made that trip. Either tracks from an earlier take, or the scene was filmed and then played in reverse, to be safe for the actor.
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.