hmm... Nice facial expression 
though the whole sprite needs work.
1-There are pillowshaded spots. Pillowshading is a common mistake by the begginers; it's when you shade near all the outline and keeps the middle bright, which makes it with inconsistent lightsource.
2-It's clearly visible that you used the MS Paint tools to make it. Don't use them if you're trying to make it look professional-like.
3-Don't use MS Paint default-ish colors. They're bad for pixeling; create your own by scratch (that means, not just darkening or brightening a default color) or if you can't do that, get a palette from the real sprite to help you up (don't forget to give credit for them).
4-You need a bit more contrast (difference between light colors and dark colors). Having two identical shades are useless. But there are some places with too much contrast (i.e the arms). Make it match with the whole sprite.
5-Work your anatomy. His arms are away from the body, his legs look a bit short and his belly looks misplaced. Also, it looks like is a different object protuding from his body; the way you shaded the belly makes it weird. You need to shade the belly and the body as one object.
though the whole sprite needs work.1-There are pillowshaded spots. Pillowshading is a common mistake by the begginers; it's when you shade near all the outline and keeps the middle bright, which makes it with inconsistent lightsource.
2-It's clearly visible that you used the MS Paint tools to make it. Don't use them if you're trying to make it look professional-like.
3-Don't use MS Paint default-ish colors. They're bad for pixeling; create your own by scratch (that means, not just darkening or brightening a default color) or if you can't do that, get a palette from the real sprite to help you up (don't forget to give credit for them).
4-You need a bit more contrast (difference between light colors and dark colors). Having two identical shades are useless. But there are some places with too much contrast (i.e the arms). Make it match with the whole sprite.
5-Work your anatomy. His arms are away from the body, his legs look a bit short and his belly looks misplaced. Also, it looks like is a different object protuding from his body; the way you shaded the belly makes it weird. You need to shade the belly and the body as one object.