The large dragon we display is an example of the Hollow-Face illusion. This occurs when you look into the back side (hollow side) of a mask. Because you 'know" that a face always bulges toward you, that is what you see .. even though that is not what you are looking at. For this to work, the parts that are normally lit from above must be brighter than those that normally have more shadow. You should notice that our dragon is lit from below with a spot light that makes the forehead and front of the face brighter than the cheek and neck.
A desk-top version of the "dragon illusion" was originally designed for the 1998 "Gathering For Gardner 3" in Atlanta, GA (2014 version). You can download a paper cutout in any of three colors - red, green, or blue. These are the current ThinkFun versions.
If you have trouble seeing the illusion, either close one eye or stand a little further away. (Hint - when taking a video, the camera has only one "eye".)
There are many variations on the dragon - such as K9 from Dr Who. Be sure to bend the ears forward (omitted from the instructions).
Another example you can make at home is the Magic Dice Illusion. (Use the second Download button next to dice.pdf.)
I made this - it works with one eye but
is a problem with 2 eyes :(
I think this is because it is too close to use both eyes. Basically, when using both eyes, large objects work better than small.
For instance, the Smithsonian has a large hollow house in the National Gallery of Art Sculpture Garden
and at Mount Vernon, the museum has a large hollow-face sculpture of George Washington.