Today's class began with this video that I was able to find fairly easily on youtube. It starts out fairly innocently and ends up down right disturbing. The point here is that children mimic us. The best way to encourage proper behaviour is to model it ourselves (and vice versa).
Obviously I'm not showing William how to beat people or smoke cigarettes, but since I've had a cold this past week, William has started ripping off pieces of toilet paper, blowing into them, then crumpling them into a ball.