You're making a lot of progress, and these have already come a long way, but you could make them even better by addressing a few more issues.
Here's a (really messy) edit. I only had time to work on the top two expressions, but you get the idea.
Main points:
-There's a lot of banding going on, mostly concentrated around the mouth. You might be tempted to think that the fuzziness this creates is good way of conveying texture, but in reality it obscures visual clarity and clashes with the shading of the rest of the sprite. The
Ramblethread by Helm has a lot of indispensable advice about avoiding banding.
-In the topmost sprite, the specular highlight in the pupils is lost in the brightest yellow color next to it, which makes the eyes appear to bulge outward. Try darkening the yellow color so that the specular sticks out as belonging to the pupil.
-You've done a good job of improving the palettes as you've worked on this, but the contrast on the darker fur palette could still be upped a tiny bit more.
I messed around with other stuff as well, but for the most part the above is all I can think of at the moment. Good luck with your game, and keep up the improvement!