I have no idea who the little boy is supposed to be. Granted, I haven't played the game and only got up to episode 3 of the anime.

that's a boy? O_O!?

The one with the hat? I think so? Is it a girl? :D

I think the one in the hat is Nagisa as a child.

So, PIME TARADOX

Nope. it's not Nagisa as a child. It's test

Fencedude said:
I think the one in the hat is Nagisa as a child.

Nope... wrong on that one.

In the main ending for clannad, Tomoya and Nagisa get married and have a child, and that's who that is