Robot Unicorn Attack is a fantastic online flash horse game, released in early February, 2010. The game became viral in 2010 almost immediately, where it got a whopping 1 million plays online just during the first week. As a result of its major success, the game company released three more games under the names: Robot Unicorn Attack Heavy Metal, Robot Unicorn Attack Christmas Edition and Robot Unicorn Attack: Evolution. The games is famous for it's specific heavy metal music being played in the background.