Perceptual Illusions
I used to have a printout of <a href="https://www.michaelbach.de/ot/mot-snakes/index.html" rel="nofollow">https://www.michaelbach.de/ot/mot-snakes/index.html</a> over my desk.  People got so freaked out by a piece of paper "moving" that there were people who literally refused to go to my desk. :-)