Pepper's ghost

Pepper's ghost is an illusion technique used in theatre, amusement parks, museums, television, and concerts. It is named after John Henry Pepper (1821–1900), a scientist who popularized the effect in a famed demonstration in 1862. It has a long history, dating back into the 19th century, and remains widely performed today. Notable examples of the illusion are the Girl-to-Gorilla trick found in old carnival sideshows and the appearance of "Ghosts" at the Haunted Mansion and the "Blue Fairy" in Pinocchio's Daring Journey at the Disneyland park in California. Teleprompters are a modern implementation of Pepper's ghost. Examples of concert illusions based on Pepper's ghost are the appearance of Tupac Shakur onstage with Dr. Dre and Snoop Dogg at the 2012 Coachella Music and Arts Festival and Michael Jackson at the 2014 Billboard Music Awards.

An audience views a stage or room with various objects in it. On command, ghostly objects appear to fade in or out of existence in the room, or objects in the room magically transform into different objects.

The basic trick involves a stage that is specially arranged into two rooms, one that people can see into or the stage as a whole, and a second that is hidden to the side, the "blue room". A plate of glass (or Plexiglas or plastic film) is placed somewhere in the main room at an angle that reflects the view of the blue room towards the audience. Generally this is arranged with the blue room to one side of the stage, and the plate on the stage rotated around its vertical axis at 45 degrees. Care must be taken to make the glass as invisible as possible, normally hiding the lower edge in patterning on the floor and ensuring lights do not reflect off it.

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