I honestly and truly believe all good AUs should be a little “”””ooc”””” in the sense that good characterisation involves understanding that changes a characters backstory and circumstances will have an effect on how they respond to the world around them
Good characterisation isn’t about creating a perfect 1:1 canon replica it’s about understanding why a character is different in your work and about grounding the changes you do deliberately choose to make in canon character traits
like okay if we're talking about this anatomically the ear holes on a human skull and a cat are actually in the same spot it's a difference in the shape of the cranium. you can see what's happening if you look at hairless cats
ears is big. so you can put the cat ears wherever you want if you start them at the same point as where the human ears would go.
just like. pull the sideburns back a little and it's fine. it's fine.
it's the best way to catify your blorbos with visible human ears. but that's just my........ purrsonal opinion..............