I of Newton - S1-E29
Revealing mistake: Set lights are visible in the Demon's sunglasses while he is wearing them and when he is not.
Tooth and Consequences - S1-E41
Revealing mistake: The glue holding the mustache to actor David Birney's (Dr. Myron Mandel) upper lip is visible.
Answer: They live in a totalitarian state where people who are deemed too smart (and therefore a threat to the authorities) are done away with. That's the point of the test, to eliminate potential troublemakers.
Brian Katcher