It's really cute! :3 Nice and simple cellshading.
As for critique, I think that you have to imagine the Furret as more of a 3D object. At the moment, the shading makes it look rather flat at some places (namely, the tail). Don't be afraid to try out more dynamic shadows.
Also, the lines look a little wobbly for some reason. But is this because you have a mouse? I personally have a tablet and have rarely encountered this sort of problem.
All in all, though, good job. :]