Now, as for the various species:
-Dog breeds are something akin to noble families or particularly insular clans-think rednecks for some of the really stupid ones. There are LOTS of them, and they tend to be nigh-fascist due to the pack mentality.
-Cats vary a lot-they can be lazy fuckers or smooth bastards, but it largely depends on the individual. They breed fast, and keep down the rats-which the rats don't like.
Again, specific breeds are clans, and stuff like the Munchkins are about as crazy and inbred as you can imagine.
-Rats are cheap labor, and mice are the same-but delicate. Think Mexican day laborer versus maid. Rats are cowardly, rough, and crude; while mice are timid, prone to flightiness and panic, but more decorous.
Both breed like rabbits, though.
-Speaking of which, Rabbits I'd avoid, because the LOLSEX angle is too easily played up; if not, I'd make them something along the lines of cheap labor, but underground. When you can't get a mole, you get a rabbit-they dig well, they can brace decently, and if they build it, it stays up.
There are entire underground cities comprised primarily of rabbits, with double handfuls of moles, etc.
-Weasels and their kin are dangerous-thugs, assassins...not nice people, and don't get started on the Wolverines, because they'll fuck you up, and maybe eat you to seal the deal. Generally kept under surveillance for just that reason, and wolverine violent crime is punished, first time, with death. Too many have fucked up, and people have gotten wise.
-Sloths are natural accountants and security guards; they can watch the same thing for hours on end and not get bored. Clever engineers have made typewriters involving minimal effort, and most bureaucracies are crewed entirely by sloths.
-Lizards vary, a lot, and tend to be more cold-blooded (yes, I saw what I did there) than mammals. They have a reputation for cruelty and violence that may be deserved.