Or HEADS as the case may be, not to mention a chunk of space rock.
Just a little insight into what I do on the margins and backs of pages that I don't use. I usually start these out just as doodles to figure out lightsources or proportions or just to get a feel for characters before I draw them and they end up like this.
The space rock is me trying to ape something I saw Adam Hughes do in one of his pieces. I really liked the tonal quality he got with his use of grey tones by going light then medium then throwing the strongest shadow smack dab in the middle. Definitely something to think about and maybe adapting to other things and see how it works for me.