My older brother has a fat little brother (me) and what he would do is chase me around and get me all hyper then tackle me and me and then he would push on my belly, and every time I would, I would fart. It amused the Hell outta me.
Or you could duct tape a narrow pvc pipe to his back and tie a twinkie on the end. then he'll run around trying to get it and get tired.
AK BC SESH