Yeah, I'm not to big on the hat. The color on the first one isnt a very good choice. But even with edited color pallet. I think the overal shape of the hat should be adjusted. It looks like you were trying to hard to get the same shape his hat wa sin from the larger picture. Which is fine, but it didn't go over so well.
I don't have time right now on this computer to actually do a real edit job to show you what I mean. But this is just an idea. Make it smaller, and more like it is sitting on the right side of his head (or your left).
look at *your* left side of the picture, and then look atthe larger picture. Make it bubble out not curve in like a banana. Then just have a tip that is turned out to the left like in thepicture. Then follow th rough with the rest of it.
Another thing. The shadeing looks kind of weird. It looks like (on the latest one that was psoted)
Its very dark around the border of the hat, and then that light green in the middle. Make it a more olive green. You could get away with just useing two differennt greens there, and the black outline.
Just make the left side of the haiir lighter, with a toutch of the darker shade in the bottom left corner going into his hair, and then a smidge of the right hand side the darker olive green shade.
Also, I think his ear is pertruding out a litttle bit to much. But that may just be the style. It also looks like you were trying to capture the same "expression" that is on his face in the sprite version. But it makes him look sad instead of quirky and giddie. You got to be carefull with your pixels in such small work, especially when you are trying to show an expression on their face. Don't try and go into detail. Like in your 2x version, you can see you tried to make it exactly like the large pictures face with your limited space.
You can get away with just a few pixeled dots in the right places and it will make it apear as if it has that face.
Also, your body. What is with all of those colors on his stomach? When you are doing such a small sprite, its hard to show all of the details in such a small area. I know. I used to have the exact problem when I first begain spriting. Because the program I used only allowed a canvas about the size of your sprite. But I would try and match colors exactly, and put in all the little details. When In fact, it just doesnt work that easy.
It is just a little sprite. So you don't need so much details. You could get away with just a smidge of beige pixels to show that little "rug" thing thats hanging over his crotch.
Overall its nto bad. Its better then when I first started. Over time, you are going to look back on it though. And laugh. I guarantee it. Becuase you will progress fast.