Continuity mistake: In the final scene, the position of the silver dollar lying next to Franklin's hand changes several times between shots. (00:23:45)
Continuity mistake: After Franklin falls through the window at the end, he lands on the pavement below - on top of the broken window frame. Next shot, when the police are examining the body, the window frame has moved out from under Franklin and is lying about a foot away. One shot later, though, it's back in its original position underneath him. (00:20:00)
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)
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.