First three frames are great, fourth needs work!
The main problem I see is his back leg is a bit too thick in the final frame. I also think it should move upwards a bit more, you'll notice its as if he's only occupying one half of the shadow he's making, because he's not spread out enough along the Y axis. In that last frame his front foot is strangely positioned as well, I don't think it should be angled like that, try his toes touching the ground and his heel raised without being angled as much towards the camera. And finally the arms are much more drastic in their angles than the second frame. Try to mirror the positions of the second frame and it will look much more natural. Glad to see this getting revived by the way. c: