Hey there, here's a short running loop I made.

http://petskii.deviantart.com/art/Cat-run-421245330?q=gallery%3APetskii&qo=0

EDIT: Added a gif

I love it when people try to animate something different than stick men, creatures and other beings :) What cought my sight was the joints on the front legs, I think they bend the other way in reality, however the thing I love the most about animating is that you can create anything you desire :)

Ok...
-The front legs bend the wrong way
-the front paw further away is short
-there is a lot of sliding during the run
-if there was a ground, it would make it better
-needs some easing, especially on the back legs
-the flow is messed kinda messed up, it seems to slow down after the first jump
-the back legs aren't on the ground for long enough
-there isn't enough force behind the back legs when he jumps to make it seem believable

I think that's it outside of the logically obvious things like color and background,
Hope this helps :)

I dunno....
it seems to slow

I feel like it runs like a dog, not a cat. Can't pinpoint why, though.

Quote from Scarecrow

I feel like it runs like a dog, not a cat. Can't pinpoint why, though.

I guess its because of the body structure and the easing, as well as how dogs seem to usually use two sets of paws to run at a time, while a cat runs with four paws more distinctively?