The Jungle - S3-E12
Continuity mistake: Richards opens the door and finds a lion on the bed over his wife's body. When the door first opens, the corpse has dark hair and the blanket is twisted and disarrayed. But when the shot cuts to the lion leaping, the corpse's hair is a lighter color and the blanket is neatly spread across the bed. (00:23:40)
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.