Very nice! =)
I love the bg simplicity, good parcimonious and efficient use of pixels.
Mr Cat's face is not very readable, but it's quite difficult to achieve at this small size anyway. The light on him is also inconsistent with the shadow on the ground. He might use a brighter highlight too.
Don't seek to smoothen all lines, some boundaries need to remain sharp: the front of his chest, the edge of his hand both are roughly vertical planes facing the light: they should be cut sharply from the bg. On the contrary, the tail would benefit from AA as it's a curve.
Ah ah, very nice ! I particularly love the puffy chest hair and the way you put its legs.
This is great! I loved the way he stands proudly :)
Nope, nothing wrong here.