Volkswagen: Piano Staircase

In 2009, Volkswagen caught people at their most musical by turning a subway staircase in Stockholm, Sweden into a giant piano when nobody was looking. The next day, each step produced the sound of a different piano key as people climbed up and down the stairs. The campaign was a part of "The Fun Theory," which suggests people are more likely to do something if it looks fun. As a result of the stunt, 66% more people chose the stairs over the escalator at that particular subway terminal.