CrowdStar , the makers of popular (on Facebook) games like "Happy Aquarium," "Happy Island," "Zoo Paradise," "Happy Pets," and "Hello City", has entered into a five-year strategic relationship with Facebook, in order to accelerate growth of these games. "As part of this announcement, Facebook Credits will be the exclusive in-game virtual currency around the world for current and future CrowdStar games," a representative for CrowdStar tells WebProNews.