When Mike is talking to Enzo, and right after lighting the cigarette, Mike seems to have an odd look, as he looks at Enzo. I think I read on here, it was because Mike thought Enzo was so nervous, yet Mike was under control.
I always thought it had to do with Mike thinking something was up, or something coming to him that Enzo is hiding something. That scene didnt sit right with me, for some reason. Or am I reading too much into it? Just seems Mike is thinking something there about Enzo.
Mike is thinking something about Enzo. But not what you're thinking that he thought. Mike realized that this boy Enzo stuck his neck out for Don Vito by not only risking his life, but also risking deportation by staying there and taking a chance at getting arressted. I believe that in the novel Michael makes sure that Enzo was taken care by the Corleones for sticking his neck out the way that he did.
As I have posted before about this scene, I feel that was the defining moment for Michael. He and Enzo face death when those cars pull up, and after they pull away Enzo, understandably is shaking uncontrolably. Mike takes the lighter and calmly lights Enzo's cigarette, and then looks long and hard at what he is calmly doing. I think at the very moment Michael realized that he could live this "life" without any problem. That he was a natural at it. I think that many things ran through his mind at that split moment. He also realized that had he not been there to stand outside and act like a bodyguard, his father would have been killed in that hospital. Mike, thinking all this knew that he now must get involved in order to save both his father's life and the family itself.