The Magic Mirror is a sentient magical item possessed by the Evil Queen in Snow White and the Seven Dwarfs. When the narcissistic queen asks "Mirror, mirror, on the wall, who's the fairest one of all?," she expects it to respond that it is she that is fairest. However, the mirror responds that the fairest one of all is in fact Snow White. The queen's jealousy leads her to poison Snow White with a tainted apple, sending the girl into a deep sleep.
In Video Games
In Kingdom Hearts: Birth by Sleep, the Magic Mirror appears as a boss when the queen grants it the power to draw in its foes and confront them in a mirror realm. In order to win, the player must determine which of the myriad faces is the true face of he Magic Mirror and defeat it.
In the original Japanese version of the game, the Evil Queen becomes red with anger which causes the Mirror to draw Terra into the mirror realm. This was changed in the Overseas and Final Mix releases, where she uses a potion to affect the Mirror.
In Wolf Among Us he helps out the other Fables with his abilities. Here he can pinpoint people's locations, but he will only answer questions if you ask him in rhyme.