This is a trope for all the times a characters' reflection in a mirror is different than what others (viewer included) see with the naked eye. In fiction, mirrors are treated as able to cause Glamour Failure in supernatural creatures, reveal Mind Control, and if the mirror is magical, reveal a character's true nature. The most common uses are revealing the true form of a Shape Shifter, that a character is a Vampire or soulless, and if a character is under Mind Control. A subtrope of Glamour Failure and Lie to the Beholder. Compare The Shadow Knows. Examples: