I like the face, it's very funny, and the line-work is smooth. It would be nice if you added values to the hair so that it isn't just black. Also, the back of his hand is perpendicular to the viewer, when it should be on the paper he's holding. I also think this type of cartoon could benefit from line-weight variation so that you can emphasize things like his expression, or his arm, which is closest to the viewer.