Volkswagen and DDB Stockholm have created a series of fantastic videos that are based on a very simple idea: that the easiest way to change people's behavior for the better is to make things fun to do.
And they prove it in a series of viral videos.
One of those videos, Piano Staircase, has achieved more than 1.5 million views since being posted five days ago.
See them all at TheFunTheory.com.