In case anyone was unaware, or too young to have followed the events at the time, you DESERVE to know about this.
This article gives a brief overview of the events (but in such a way that spoils some of the surprises): https://cargocollective.com/GaryRosen/The-Dark-Knight-Known-as-the-best-viral-movie-marketing-campaign-in
I remember following live updates on R*ddit. It held all the tension and spectacle of a breaking-news emergency, except it was GOOD and FUN. When they found the cake, and then they reported what happened next, I ascended to nerd nirvana. It was magical. MAGICAL.