you could make the mouth more consistent. there're two frames where there's a "lower lip" type thing going on (10 and 18 in the sheet), where the bottom juts out a bit from the rest, and it makes the animation look strange, as if it's trying to say something.
I think there're also too many frames as it's spinning away and toward us...it seems to spin more "quickly" when we're seeing its bottom or top because there are less frames there in comparison, and thus it makes it look jerky.
I think there're also too many frames as it's spinning away and toward us...it seems to spin more "quickly" when we're seeing its bottom or top because there are less frames there in comparison, and thus it makes it look jerky.