The greenscreen is noticeably darker at the bottom, so you should try to even out the lighting. There's also a dark crease running horizontally along the bottom.
Some of the edges in the comps are a little soft, and it looks like the girl's sweater has gone a little transparent, so you might want to check your key settings. When filming it might be best to frame the puppet really tight? I may be thinking about this wrong. I am going from my experience with image manipulation. With an image you can normally shrink it down and the quality is still good but when you try to enlarge it beyond what the original size was it tends to get fuzzy. Now with the age of digital video that may not be as important.