I kind of like this a lot. The kid has a lot of charm, however a lot of contrast issue as well(All I can really see at first glance is a bright blob of pixels. Colors don't immediately break apart the various definitions of the sprite like they should. It's a lot of similar colors going on). I also like the crow. On the animation, the hair is way too exaggerated. 2-3 pixels of movement translate to a lot of distance at this resolution. Could be toned down a lot and still have the effect you're looking for.
I think the weakest is the rhino. With the larger size, the style doesn't convert very well. It looks very unrefined and the simple shading doesn't help portray what needs to be communicated. Also, the head is WAY larger than the body. This can work with humanoid characters because of the weight is distributed amongst the body, thus we can picture it working out physically. However with a horizontal build like that, the first thing I think is... "whoa, how the hell is it holding that thing up off the ground?"
Cave Story is a game with the same resolution and simplistic style, yet it manages larger sprites(much larger than the rhino) very well. It may benefit to take a look at that game to see how it did things.