Well, I like this. Your little guy's got some character. The blue leg in the run cycle is a little odd, it looks like it just jumps from the very back to the very front, I'm not on my own computer and I've got no graphics editing programs here but I would guess moving the passing position of the right foot forward slightly would help the transition from the back to the front. I also don't think you really need to shade the black, it looks fine as it is IMHO. The rounded floating platforms look good, but I would put him in front of them, instead of behind them.

That zombie looks REALLY familiar to me. Should it?

(Edit: To infinitegames-- I think he said he's only got the JPGs.)

That's pretty painful to be honest. It's really cutting into the readability of the cat. The mouse is almost invisible too. Tone down that lighest color in the background, and knock the saturation down. Right now it's maxed out. You might want to do something about the floor as well, it's about the same brightness as the cat's paws and so they really get lost down there.

Aw man, NaCl beat me to the punch. I did a quick edit here for you also to give you some ideas.



Pulled both his shoulders back to give him a more natural pose (as NaCl mentioned).
Added a few colors plus some shading.
Nixed most of the interior black outlines--This helps a lot in giving you more room for little details, the black lines running everywhere really break it up and take up a lot of sprite real estate without actually contributing much to the details of the sprite.
Rearranged the feet a bit to give him a more solid stance--it would need to be fiddled with a bit to give him a run or walk cycle.
Gave him some yellow rubber boots, just because he looked like he needed some.

For some reason, it makes me think of South Park. Not sure why. Maybe it's just the whole little kid dressed up for winter thing...

I think the boobs need a... boobjob. And not the kind of boobjob that makes them bigger. They kind of look like dangly grandma boobs that have been filled with helium. I think it would help if they hung down a bit more naturally and were more attached looking at the bottom. Fineart.sk could probably lend you a little help as well.

Here's a quick edit I did, feel free to ignore all the anatomy changes I made except for the boobs (which aren't that great anyway, just a quick example). I was just dicking around and I don't think it's really correct at all. :-P