Other mistake: When Lillian calls Oliver, she tells him that the car stalled at 3rd and Park - the original scene of the accident. Later, when Oliver goes into his garage in the middle of the night, the car turns on its radio and goes to a news broadcast about the hit-and-run that took place at 3rd and Elm.
Continuity mistake: After Oliver hits the bicyclist, the bike's front wheel is turned upright, but is still intact, and the boy has been thrown across a lawn to the edge of a phone booth. In the next shot, however, the wheel is suddenly crumpled, and the unconscious boy has somehow moved to a completely different place on the grass, several feet away from the phone booth. (00:01:00)
Continuity mistake: At the beginning, The main character is driving a car and hits a bicyclist and kills him. The inside shots from the car show the driver's window closed. The outside shots show the driver's window open.
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.