This takes a little time, but is totally worth it.
You know those old 3D images where you have to intentionally unfocus your eyes, and you see an image of a dolphin or a train or something? This is similar, but it is a movie!!!!
If you let your eyes go unfocused you can see a cool little clip of a person goofing around on the internet!
PS -- It took me a full 5 minutes of trying before I was able to "get it" -- feel free to post your comments with how long it took you!