Yeah, I think that "Blink" went a long way, in just one episode, in establishing who Mac was, and why, for the most part. And the fact that a comatose woman who would never be conscious or speak again is the only person he told some of his secrets to, was very telling, as far as where Mac's head was at that time. I think we started seeing Mac come out of his shell back in S1 though, in the "Recycling" ep, with the dog show. He was actually laughing and enjoying himself, and I loved seeing he and Stella share hotdogs and laughs at the dog show, in the end. I think Mac slowly but surely evolved from that point on to the "lighter" Mac that we have today.