For a simple device that will allow you to pull a rabbit out of an apparently empty box, you will need a cardboard box, a mirror, and a rabbit (or whatever you care to make appear).

The figure gives the design. Looking in the front flap, the viewer sees the bottom of the box, and its reflection in the mirror. The reflection should look like the back of the box, so the box appears empty. The deception works best if the inside of the box has a pattern, designed so that he edges of the mirror don't stand out. Shadows may be a problem - a bright light source or lots of lights in the room work best. You first open both flaps to show that the box is empty. The top flap must be opened symmetrically with the front flap so that the viewer believes that the front flap's reflection is actually the back flap, and the she can see right through the box. (Place your two hands symmetrically, one on each flap.) Do not allow the viewer to look in the top opening. You then close the front flap, reach in the opt flap, and pull the rabbit from the `empty' box.