A holographic illusion (for example, in the toy called a "[url=http://www.amazon.com/Toysmith-79747-3-D-Mirascope-6/dp/B000N5T8KA]3D Mirascope[/url]") can be produced by joining two parabolic reflectors.

In the illustration, the red points can be moved to change the shape of the parabolas. The foci of the parabolas are marked with x's. The frog can also be moved.