I know of an anime movie by the creator of Spirited Away and Princess Mononoke about Cats it's called " The Cat Returns" I own the Japanese import but I haven't watched it yet as I can't understand enough Kanji to now how to turn the english subtitles on but it's a about a human girl who falls in love with the Prince of the Cat kingdom and he takes her there and she starts to become a cat herself. I'll let you know more about it as soon as I watch it today.
