Lunchtime Value Drawing

I worked on a value drawing at lunch, today, of Marvin.

The point is not to get an exact drawing, although I confess that I worked quite a bit at this one.  The point is really capturing the values.  Still, there's something not quite right about the face shape and I can't quite see what it is.

This seeing stuff is hard.  With the position of the picture and the drawing, I can see places where the values could be better.