There's a few on there that aren't roiding. Edward Norton for example doesn't look like he touched roids, just spent some time in the gym.
It's hard to tell with guys who aren't athletes and don't have the massive amount of veins like Carrot Top does. Norton is probably legit because if you stick to a strict diet and a competent and professional workout plan it isn't unreasonable at all to think he put on 30 pounds in three or four months. Bale's is.. odd just because of how insanely skinny he was and that awful diet he claims he used to gain back the weight. More importantly I would hope he didn't use steroids because I'd hate to think of the damage his heart and other organs went through losing all that weight for the insomniac movie then possibly using steroids while gaining 100 pounds in less than six months.
I think 50 Cent was on steroids and came off of them. If you look at him when Get Rich Or Die Tryin' came out he was extremely ripped and now he's like kind of flabby. And Nelly I could see gaining some muscle but when from really skinny or big and ripped seemingly overnight when makes me think he had a little help.
Unfortunately, I now know the answer to the question, "Does Carrot Top's carpet match his drapes?". Damn you, ADP. Damn you to Hell.