He recorded himself walking backwards in Tokyo, and uploaded a reversed version.

The result was brain-damaging! Try watching this normally first, then try to imagine how he did it. It'll twist your brain a bit, but you'll get there.

The video is called "Tokyo Reverse" by Simon Bouisson & Ludovic Zuili, the duo are known as SANDL. They're french directors doing different short at different places for commercial, documentaries, and such.

Check out their website for more.