A few days ago a post appeared on the Something Awful forums noting a curious website called Notes to Mary. The notes are a series of threatening letters from a high schooler named Robert to his crush, Mary. The goons figured out pretty quickly that they had an ARG on their hands and went to work on solving the puzzle. Several other forums picked up on the game. Robert began interacting with players, sending them strange messages and several series of numbers that appeared to be some sort of code. A Flickr pool was started. Players even created an IRC channel to swap clues and information in real time. The Notes to Mary site offered a link to a login. All effort was made to crack the user/pass combo. Finally, several days after the game began, users were finally able to log in. The game was solved. The players would be rewarded for their hard work. Where did the login lead? Here.
"Robert" had just pulled off the most epic rickroll in intertubes history. The author of the game had never really intended for it to be a game at all. He just thought it would be funny to put up some creepy notes and see what sort of attention they got. When SA goons decided it must be an ARG he decided to play along. The numerical "codes" he sent out? Random numbers and dates plucked out of the air. Three hours before the solution was to be revealed he set up the redirect to the rickroll video.
[Hat tip: Bryan Alexander.]