The VG Resource

It shows promise, but the lineart's a bit dodgy, and you're missing a few frames.

Something about it feels metal slug-y. That might be a good direction to go in. But for now, Sprite Discussion.

that bullet bill needs at least three more weeks of reworking its rotation and actually give it proper highligh that doesnt spin as if it was painted over it.

not to mention the tail of the bullet bill is suposed to spin too.

metaru just basically summed up what I was thinking
you need to either
a) add more frames
or
b) completely redo the spinning
because it looks really choppy as it is.

and fix the shading as well.
the highlights and shadows shouldn't spin the entire way around the bullet as if they're actually part of it.

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.