Alternate reality game

An Alternate Reality Game is an interactive narrative that uses the real world as a platform, often involving multiple media and game elements, to tell a story that may be affected by participants' ideas or actions. Halo has had two ARGs: I Love Bees and Iris.

Iris
Iris was a Halo 3 viral marketing and public relations campaign. It was designed to give people more information on how the great conflict behind the Halo franchise all began, as it builds up to the climactic conclusion of the series on September 25, 2007, the release date of Halo 3.

The campaign ran for several weeks throughout the summer and promised to be a compelling experience to uncover valuable information. Users who helped to unlock key information were awarded with t-shirts and other small prizes. Unfortunately, Microsoft wouldn't say whether there would be any other rewards for participating.

I Love Bees
During the summer of 2004, the website ilovebees.com was used as a publicity site for Halo 2, with the site being pointed to by adverts for the game during movie trailers. Ostensibly a beekeeper's personal site, the server appeared to have been taken over by an unstable A.I. whose thoughts are scattered on the site.

The front page had a counter counting down to July 27, 2004 (when it says "network throttling will erode"), August 10, 2004 (when "this medium will metastasize"), and August 24, 2004 (at 8:06 am, when it will be "wide awake and physical") - many thought something big would happen related to Halo 2 on these dates, however it was only related to the ILB game. Currently there is a counter counting down to the day the Covenant will attack Earth, over 500 years in the future.