Michael stalking Tommy

Good question. I don't know why he was stalking Tommy, since he never seemed to go after him or Lindsey.

He may have recognized him as the kid who was with Laurie earlier that morning when she dropped the key off.

"Does Michael see Tommy as a reminder of himself as a kid"

That's what it seems like to me.

I've wondered about this too.

I've come to the uncharitable conclusion that it's a throwaway scene that's added just for atomsphere, to build suspense. It also reinforces Tommy as a kid who is terrorized by the idea of a bogeyman, which pays off later in the film (a couple of times).

To force the audience to come up with random speculation, such as "it reminds him of himself when he was a kid" -- if that was the intent -- is just lazy. (Ok, so if it reminds Michael of himself as a child -- so what?).

The scene also breaks the continuity of his stalking Laurie. Are we to suppose he's bouncing back-and-forth between the two at their respective schools all day? For what purpose?

Granted, Laurie and Tommy were the first two people he saw after returning to his home, but he definitely seems to have a proclivity for targetting teenage girls who were his sisters age when he committed the crime of murder as a young boy.

I think it makes sense. The first time he saw Laurie that day, (after so long if you want to buy the sibling relationship), she was with Tommy, so he was linked as part of that world. Or, if you want to ignore the sibling relationship, we could say that the dynamic still reminded him of himself and Judith. Maybe he went after Laurie because he assumed she would be negligent like Judith was in his mind. So maybe he thinks he's protecting Tommy, or preemptively punishing Laurie for her sins. Maybe he follows Tommy to see where he lives. Regardless, stalking is just what Michael does. Before killing.

Sidha108, I don't think that Michael is stalking Tommy. He just happens to walk past the elementary school when its students are being dismissed, and later wants to be in his original neighborhood, where the boy coincidentally lives. As a stranger and radically different person, Tommy does not reflect Michael. Also, the slasher would not want to share his character and skills. He briefly and weakly does it in part four, but that seems to come from an accident.