Nice trick and a cute puppy. With all that hair it would be easy to hide a camouflaged attachment strapped below the dog's mouth that temporarily "takes the place of the mouth." It's most likely a small servo device that's activated through a remote, wireless connection. If you take a look at his hands he almost always has them slightly cupped, probably a small cable down his sleeve attached to his fingers that pulls a temporary-switch activating the open/close motion.
I feel a lot more like I do now, then when I first got here