Most popular alternate reality game (ARG)

Why So Serious? was an alternate reality game (ARG) created by 42 Entertainment as part of a viral marketing campaign tied to the release of the movie The Dark Knight (2008). The game, which played out over 14 months and recruited more than 10 million players, encouraged gamers to dress up as The Joker and become involved in a fictional election campaign for the film’s District Attorney, Harvey Dent.