The upside down girl seems to be a lovely, normal human. Turn the same photo right side up and YIKES, she’s a monster! Called the Thatcher Effect (after a famous portrait of Margaret Thatcher was manipulated in a similar way,) this illusion surprises us (and creeps us out) because of the way our brain evolved to perceive and recognize faces. People who suffer from a face blindness condition don’t experience this effect. Want to see more strange examples of the Thatcher Effect? Click here.