I was on adderall at the time, and simply got lost in the drawing for 13 hours. I don't remember drawing it most of the time, just mental snapshots. I think I drew whatever was on my mind.
It was Christmas break, and I was bored, so I started drawing. With my stuff it's usually a hit or a miss, and I actually managed to hit one I like with this, so I kept it, and put it on.