BENTONVILLE, Ark. — Of all the mobile games out there, perhaps none is as popular, or addicting as Angry Birds. And the Angry Birds phenomenon doesn't end with digital games; plush toys, board games and costumes have all been inspired by this app. As the world's most-downloaded mobile game, it is no surprise that Rovio Entertainment would want to team up with Walmart for the newest version of Angry Birds, which will be released in app stores on March 22.