Kyle and Stan

This looks nice and well composed- the expressions are good and I like how you designed them.
The hair is perhaps lacking in differentiation in value compared to the skin because you definitely varied in tones with the skin. The top half of the arms are a bit too long- the elbow should tend to be at the top of the head when held up.  I would maybe give some variation also in the line weight, but this is a stylistic choice anyway so either way is fine~
Did you use toned paper? Toned paper is one of my favorite things to work on. : D