This is my favorite look for Don - the 'fro and beard. SO masculine, edgy, and sexy.... as long as it didn't get TOO big - for a while it was so big it looked about to tip him over.
He is very adamant that he did not have a perm. However, I think he grew his hair out like that to hide his ears. He was quite self-conscious about his ears sticking out when he was younger, and the fro nicely covered them. Of course, once he had money, he got them pinned back.