When I was a kid, my best friend Ally and I would run around with the older boys on the playground during recess. There was this group of boys who were one year above us, and they carried this red felt-tip pen around that we dubbed "Red Pen Man." Really, at this point I have no clue what made us call it that or create its very own storyline. Anyway we'd decided that pen was evil, and so they started also carrying around a blue felt-tip pen, or "Blue Pen Man." Blue Pen Man was our hero, and fought Red Pen Man on a regular basis.
At some point, obviously, we stopped playing that game. I don't remember any of the details. I just remember Red Pen Man and Blue Pen Man--the devil and the savior in pen form.
It seems like those are the two necessities of any proper story.