ahahahaha - So, sometimes people might say 'mouses' or 'meeces' if they are being silly, especially if they are being cute, or mimicking little children excited about a cute thing.
Like: EEEEEEEEEKKKK - Look at that ALL THOSE little ickle weenie MEECIE MOUSES!!! Wearing SPECTACLES!! Reading Kafka! And look at their wickle MONOCLES!
Bureaucratic mice!! I can see that, yes, with their nose in the air, reading Russian literature and drinking teeny cups of tea. The rats are more anarchists, listening to punk rock and swigging whiskey straight from the bottle - those tiny bottles you buy on trains or planes.
And you have the makings of your next horror story right there. The Anarchist Rat vs The Bureaucratic Mouse. How is that going to be horror you might wonder.
The same way forgetting to pick up your wife is every man's worst nightmare :D
I do think you can write it in a much better and funnier way than me!