[@Kafka Komedy] So frowned upon it's unheard of. If you live on the border of the kingdoms, you regularly deal with rats raiding your village, stealing your shit, and eating your babies. If you'd like to explore this relationship (Secret enemy friendship comes to mind) I could see a lot of ways to make it work.


EDIT: Also, they mostly don't deal with other rodents. Voles, shrews, moles, and hedgehogs play the traveling merchants, dignitaries, and otherwise foreign-guy-escort-mission characters. They're there if you look (wish to include) playing minor roles, eating funny foreigner food, having accents, and not participating in mouse democracy.