DDB Stockholm created a great social experiment for their client VW. They modified a set of stairs in a Stockholm subway station so that each step functioned like a piano key. The best part is that the stairs are right next to an up escalator. Before the change few people used the stairs. After the musical enhancement 66% more people "played" the stairs vs passively riding the escalator. This is experiential marketing at its best. Make subtle changes to deliver a point, in this case an everyday act like climbing a set of stairs can be the high point of your day. I suppose they can try to correlate that to having fun while driving via a VW somehow. 

The campaign also allows folks to enter their own fun theory ideas to potentially win a prize.