Marni Rose McFall is a Newsweek reporter based in London, U.K. Her focus is on U.S. politics, social affairs and popular culture. She has covered fashion, culture, art and music extensively.

That is Young-hee, an innocent-looking robotic doll who has a deadly role to find contestants to gun down playing the game "Red Light, Green Light" if she spots them moving. The doll, who is clad ...