OT, maybe Cat shapeshifters

We rescued three kittens on our June 27th anniversary. Two are brother and sister littermates, one is a red and white bobtail mix. Watching them and getting to know their individual personalities has offered us hours of entertainment.
And naturally, I've been thinking about writing a cat shapeshifting story.
I've found three brief references to Celtic cat myths and one of them may just be the one I'm looking for.
So many stories, so little time!