 The dragon optical illusion in this video is pretty cool. The website it is from even has a PDF you can print out and may one for yourself. The basic principle of the illusion is that depending on which angle you look at the dragons head it always appears to be looking straight at you. This is accomplished by the fact that the face of the dragon is hollow and we mis-interpret what the actual shape is. According to the website the dragon was designed by Jerry Andrus and he calls it "Eye-Foolery".
Check out the paper dragon for yourself. Source: Grand-Illusions.com | 
