His arm snaps suddenly forward from, like, vertical to horizontal. Also, some head movement side to side and body-bobbin up and down would give this some more character and naturalness. Also, his legs seem to change width. I suggest making the farther leg darker to avoid confusion as well as moving the near leg back about a pixel during that idle(?) frame. The colors on this are good and strong, and the head looks very nice. One more AA shade on the torso couldn't help.