In-game mobile advertising may still be non-existent, but big brands are increasingly using the game format to promote themselves to mobile users in other ways. Burger King Corp. has announced that it has partnered with Mobliss in developing and selling a series of mobile games using BK-branded content. The fast-food chain’s first game will be out in the Spring of 2008 and will involve players vying to become “the King’s” protégé by passing through a series of challenges in a BK-themed city. BK has already developed three XBox games for Microsoft (NSDQ: MSFT) and has a number of product placement agreements in place for other games. BK will plug the products in its restaurants and packaging, and customers can download and purchase them through texts. The games are being published by Mobliss, which was also behind the text voting service developed for American Idol. Mobliss has direct publishing agreements with Sprint (NYSE: S), AT&T (NYSE: T), U.S. Cellular, Verizon (NYSE: VZ), Alltel (NYSE: AT) and T-Mobile, so the games may well get promoted on-deck too. (release)