I luv this li'l guy!
Wings are blocky. Too much contrast/ too many shades.
Looks too dark around the edges. Other than that, I can't see anything wrong.
I'll probly just keep the 4 shades he has cuz he isn't a small enimie or anything like that. but I did try making the wing look less blockey by taking a pixel from in between the wing and the body.
It seems pillow shaded on the head and arms. :p
Nice shape. But the shading needs to be less scattered. Use a yellow that has more contrast, like Koopa's yellow.