"I never get tired of Brusspup's Amazing Animated Optical Illusions series because I love making my eyes feel dumb and in turn making myself feel even dumber. It's always good to humble yourself with optical illusions." So starts the post on Gizmodo's Sploid. "Especially optical illusions that seem to be animated to move but are actually just well designed images. The lines in the transparent sheet create movement when passed over the image. It's a neat trick." Read and see more.
A larger variation of these illusions can be found at http://www.scrollslowhavefun.com/.