Hmm, this is super cute. And I love to see South Park fanart!
Anyway. The biggest issue here, for me, is the legs. They are too long. His torso is also a bit too long, as well, but that could just be an illusion based off the elongated legs. Another issue is the feet. Is there one or two feet there? Try and define your lines a bit more. I know it is difficult to do so with a pencil. I always have to go through and redefine my lines whenever I'm sketching or drawing on paper.
Everything else is pretty good. The face and jaw are a little awkward, because one eye is bigger than the other. And the ear looks strange. You should put a little more definition there, as well. Try to make it look like the ear and the jaw are two separate forms.
I really like the hat he is wearing though. You did very well on that!
Good luck and I hoped this helped!