Milly and I would like to recommend for your viewing pleasure Miss Minoes (2001), a Dutch film based on the children's book Minoes by Annie M.G. Schmidt (published in the United States as Minnie; Milkweed Editions, 1994). I love the premise--a cat turns into a young woman, instead of the other way around as so often happens in fantasy books. And I love Miss Minoes's green fur-lined coat.
But back to the premise. It's a fun one for cat-lovers in particular, as Miss Minoes retains a lot of her feline qualities: she climbs trees, rubs noses, hides under the table, sleeps in a box. She purrs even! There's a plot, too (it involves a shy newspaper reporter), but it's the cat-as-young-woman part that makes me want to track down the book, which is bound to be better than the movie. And to ask about other children's books featuring animals that turn into people (not just anthropomorphic animals, which are a dime a dozen). I know there must be lots.