The Trouble with Templeton - S2-E9
Continuity mistake: At Freddie's speakeasy, when Laura lifts Barney's script from the table, she begins to fan herself. In the wide shot, the script's titled top page with corner diagonal stripes is gripped under Laura's four fingers, with the blank back page at her thumb. It cuts to a close-up, and now the script is gripped in Laura's hand the opposite way, with the top page at her thumb (the back page is blank).
The Trouble with Templeton - S2-E9
Visible crew/equipment: When Booth walks over to Laura and Barney at the speakeasy, the moving boom mic casts a shadow on the wood pillar behind Laura, at the top left side of the screen.
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.
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.