To celebrate the sponsorship of one of the most important gatherings of independent filmmakers and fans in the world, Diet Coke launched an innovative, non-traditional campaign throughout Tribeca to the movie-loving people of New York.

Out-of-home billboards were crafted in the language of film—in this case, the screenplay. Posters and wild postings instructed people to tweet the hashtag #ThePosterMadeMeDoIt and an ad in TimeOut NY told people to tweet #TheAdMadeMeDoIt. Anyone who used the hashtag ...