Look up Belgian Blue Bulls, like the one on Bigger, Stronger, Faster. They have a genetic defect causing them the grow twice the muscle. They're pretty insane.
Yeh the dog was definetly legit. We had a university lecture on this the other day, really interesting stuff. If legit myostatin blockers ever do hit the market...well, who knows what will happen. It could potentially transform not only the industry but the whole community. Every high school kid will just go for those rather than gear and they won't even have to go to the gym to gain massive amounts of muscle anymore.