This is a famous optical illusion called the “Dragon Illusion.” Find out how to make one of your own here (just pick your color, print it out, fold, cut, tape, etc.):
http://www.freewebs.com/dragonillusioncolors/
Find more optical illusions here:

http://www.grand-illusions.com/opticalillusions/
Read about a recent prize-winning illusion here:
http://scienceblogs.com/mixingmemory/2008/06/cool_visual_illusions_rotating.php
And here’s a recent touch-based illusion:
http://web.mit.edu/newsoffice/2008/touch-0717.html
Fun.

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