To help drive home the point that you shouldn't ruin a movie by talking, using your phone, or snacking excessively loud, Coca-Cola created a fake movie trailer featuring people in the actual theatre disrupting the action on screen. It served to drive home the clip's tagline: "When you make noise during the movie, you become part of it."
Using a green screen and a hidden camera in the theatre's lobby, unsuspecting patrons were filmed and then immediately composited into a fake trailer that served as a PSA reminding the audience to be polite and respectful to others while enjoying a movie. The turnaround time for pulling off such a stunt was incredibly tight given the clip had to run before the movie everyone was going to see, but there's no doubt it would have put everyone in that theatre on their best behaviour. [YouTube via Taxi]