Someone stop me before this spins off into a third storyline focusing on these two.
It was very important to me that Felix, who I imagine having a deep voice before, sound positively adorable in this form. I don't know exactly what she sounds like and I don't want to decide for you, but I'd bet dollars to donuts there's gotta be SOMEONE on My Little Pony who sounds like her now.
I was originally going trying to find a good gender neutral name that had something cat-like about it. but I ultimately went with Felix because Felix is a fairly masculine name and, spoiler warning, she might ask to be called something else fairly soon.
The most difficult part of this comic was figuring out how to have Kitty reach the conclusion that she had done this, as people can easily cast their spells for the first time without feeling a darn thing. I've decided there IS a sensation, BUT it's brief, and the sort of thing one can easily miss if something doesn't draw attention to the exact moment it happened (sort of like slight chills from listening to a particularly rad song or something like that).
I'd say turning your platonic guy pal who's normally taller than you into a busty cat girl maid who's shorter than you and pretty much exactly your type would qualify as drawing attention to that exact moment.