^^' It'll sure take me a while before being able to draw one character over and over like that... Wonderful job on all of them! My favorites would have to be the 'tired' and 'irritated' expressions. ^^ they're such realistic expressions.
I wanna say your expressions are perfect and I know this is probably a sketch of random expressions not a full fledged picture but the shoulders are a little unproptinet but besides that its verry good