pretty smooth animation. Looks like you have some stray white pixels around the wrists though
Nice little sprite. Might I suggest you try doing some selective outlining on the inside lines? It can help to give the piece more depth. And I would also suggest removing dithering, as it doesn't have much of an effect on such a small sprite, and just adds noise to the picture. The teeth also might look nice if they were less subtle (an the different color there is a little odd). If you'd like me to show you what I mean, let me know. Keep it up 
I don't know if this is of interest for you but at first glance I thought it was a robodude. Probably because of the overall squarish look. Might just be me, seeing too many megamen lately...