I converted cats into a civ and created a civ composed of large intelligent rhode island red chicken.
The cats are tiny well equiped knights, they carry tiny versions of larger weapons and toothpicks.
I haven't changed their creature attributes much aside from giving their front paws graspers and removing stance from front paws (to make them bipedal), but they still have size 5000 which puts them at a massive disadvantage in combat.
I also made them goblins nemesis ethics wise, so the two are always at war and it somehow stays balanced in terms of kills to death and they stand toe to toe in arena.
The chicken carry cartoony blunt weapons, rolling pins, frying pans, brooms and sticks. As a ranged weapon they have silverware drawers and cutlery ammo that use throwing skill. They are size 50000 and have grasper tags on their wings (they are no longer fliers either).
They are vegetarian and have pretty strict ethics about it, which is why they are almost always at war with cats, humans, goblins and other carnivores and are in most cases superior to the races they are at war with.
Both civs are fully working, they wear clothes, open doors, talk, interact and everything just like a normal civ.
Then there was the slade kitten megabeast... that was fun.
The announcements and name generations on those were the best, I should add that back to the game at some point.