And after having
put up a poll, I now go and completely disregard everything and name the ratties:
Rukia, Renji, and Byakuya!
They're probably end up just being Ru-chan, Ren-chan, and Bya-chan or something.
I originally was going to go with the Furuba trio, since it was so awesome and had the bonus of an actual rat in there, except Fuu-rat (oh, there will be so much confusion with Fool-rat! Maybe I just go with Fuu...) ended up being much more aggressive than he previously seemed to be, and didn't end up being a good Tohru.
So I went with Renji, Rukia and Byakuya, because it totally amused me to think of the small, cute-looking rat with the secret streak of aggression being Rukia. And then I thought about spelling out Byakuya to the vet every time. Then I almost changed my mind. Then I realized I'd already started thinking of him as Byakuya.
Yay new ratties!