There´s something a little wrong with his pants, the shape isn´t quite right. The area of his crotch looks like a ball, and it sure is weird. I guess it´s a lack of the shadows concerning sharp wrinkles of the cloth. The kind of shadows you did to his shirt are the ones missing. Or maybe the "baggy spot" is a little too long, that might be the case too.
Also the way his glasses are done annoys me a little too. I mean, they couldn´t be totally covered with hair. The hair on the glasses looks like an "iron curtain". It also makes the hair look a little bad.
Otherwise very good work, you did a great job picturing his personality and the usage of colors is as flawless as always.
I really enjoy your works!