This is a minor thing that bugs me whenever I start thinking about it.
Above is Mousecedes King, a character from Monster High. She's referred to as "Daughter of the Mouse King"... Mouse King????
It always bugs me when people mix up that reference, there are no "mouse kings"! Okay, technically a rat king is a myth, but the fact is that the character they mean to reference is The Rat King. A multiheaded rat. Not a mouse. A rat.
This got me thinking as to why they could change that. Was it an honest mistake? Do the writers not know their error?
I usually arrive at the conclusion that it is simply because rats are not marketable. For whatever reason, mice are considered more "cute" and less "icky" than rats.
For one she lives in an analogue of New York (Boo York, because this is where puns go to die). What is one animal that is well known thrive in New York? Rats!!! You don't hear about giant mice living in New York, you hear about rats the size of house cats (even though that is an urban legend, New York rats might be on average a little bigger simply because of access to plenty of food, but they are not giants).
It reminds me of how if you do see a rat in a show it's usually evil. Rats are villains, and mice are the good guys (I've had both, I'd rather trust the Rat King)
It just seems so weird that in a franchise with vampire, werewolves, gorgons, zombies, and all other kinds of beasties, that rat would cross the line. Like sure, we can have a character with visible facial muscle tissue, but refer to a character as being part rat? Gross!
In my heart I call her a rat, because that's what she is! She's a New York rat, and that is nothing to be ashamed of. It will just never stop bugging me!