Pepper's ghost

If you want a hologram of eg Frank Sinatra for a party, a company called Musion can provide it. Holograms work on the principle of Pepper's ghost and that, as you may know, works like this:

The viewer looking through the red rectangle sees a ghost floating next to the table. The illusion is created by a large piece of glass situated at an angle between viewer and scene (green outline). The glass reflects a room hidden from the viewer (left), sometimes called a "Blue Room," that is built as mirror-image of the scene.

Could be a thought for Halloween?