The Invisibility Mirror is a mysterious mirror and the eponymous object in the Goosebumps book "Let's Get Invisible!". It is a floor-length mirror with a lamp at the top that Max and his brother Lefty discover in their attic. When the lamp is turned on, whoever is standing in front the mirror turns invisible.
At first, Max and his friends have fun playing with the mirror, but they soon realize that the longer they stay invisible, the longer it takes them to reappear, and that invisibility makes them feel strange. To Max's horror, he discovers that if someone stays invisible too long, they are pulled into the mirror and forced to switch places with their reflection. Even worse, some of his friends have already suffered this fate.
Max's reflection tries to force him to switch places as well, but Lefty accidentally breaks the mirror, saving Max and bringing back his trapped friends as well. However, later Max notices that Lefty (who is left-handed) is suddenly right-handed, implying that his reflection has successfully switched places with him permanently.