SQUASH AND STRETCH man. exagerate every pose to the most ridiculous degree. see how your torso there has the same width and height on all frames? that's not enough for a cartoony walk.
also, hold the ridiculous pose where he's making contact on the floor a lot more. make it akwward, make it look awkward for the rat to do that, make us pity him. FEEL awkward while drawing it if you can

here's my rushed edit after some fiddling, just dragging and dropping stuff, mostly extended that awkward contact phase I told ya :p. you can push it more, read up on that
survival kit and really feel the rat's awkwardness (just guessing...he's sneaking by a cat right?)
have you guys ever tried going to ggale's options/tools and unchecking "not erease image under selection"? I find it makes stuff like this a bazillion times easier and cleaner.
BTW, what I did was exagerating the motions you had in there, you're doing great laying out all the animation =)