This kid was originally written to be male, but the gender's not story-significant, so it would take less than a minute to adapt. Everyone is welcome to give it a go! Jack encounters them early in the script, tagging up a building with "Beware the Man in Black", a rallying cry that reoccurs throughout the series several times, by those who believe the Man in Black is doing good. It's not in the episode, but in my head, this kid has a rough home life, possibly facing some really abusive situations. So, they want to believe that someone's out there who might stop the bad things from happening to them anymore.