Marmaduke is a couch dog that has grown into a large animal far beyond the size of a standard couch. On the one hand, he loves fun and trouble, but deep down his heart, he feels responsible for his guardians, whom he loves most in the world. One day, a series of his antics in the form of a video goes to the Internet and makes him famous at lightning speed. A big dog with an even bigger heart becomes interested in the world-famous trainer, who makes it a point of honor to teach his quadruped acrobatic tricks and iron discipline. The life of Marmaduke and his human family will be taken over by the world of purebred dog shows and a whole host of wet-nosed canine beauties and grinning rivals. Will the barked hero believe in himself and win the title of the best pet in the world?