My son has weekly math lessons at our local Kumon affiliate. The waiting room there provides a mixed bag of sketching opportunities. If it's a full house, I usually resort to doodling robots or what-not, anything to keep my eyes on the page. God forbid I talk to anyone. In close quarters, it's a little rude to openly sketch a stranger. It can be pretty invasive. There's usually a bunch of kids fighting over toys on the floor, but being the creepy guy in the corner drawing other peoples' kids opens up a completely different can of worms!
Above: a thick mass of hair propelled by skinny little legs. In high school, I would've given this a title like- "loneliness" or "lost in thought". Over the years, I've become an expert at the 3/4 angle-from-behind view, it's much less confrontational.