Dionysus: What about those shakes that weightlifter guys drink? The only make you put on muscle if you lift all the time.....otherwise, they just make you fat. Maybe you can put on a little weight with a balance of shakes/lifting?
Along those lines..what if you just want your butt to be bigger? My hips are normal, and my butt isn't flat, but it could be poofier. I don't want it so big it could be used to sit your drink on,but a little more back there would be nice.