"The Three Lives of Thomasina" (1964). I cried my eyes out over this movie when I saw it when I was a kid, (It does have a happy Disney ending). The image of cat heaven, with the Bast statue and the hordes of Siamese cats, made a major impression on me.
But what I liked even better was the book: "Thomasina, The Cat Who Thought She Was God". It's very mid-century in its post WWII neck-and-neck race between atheism and Christianity, but then the author leaves all conventionality behind as he heads into very pagan territory. Bast grants prayers too, as it turns out.
Check out the review entitled "Cat Magick". Quote from the review:
"I first encountered "Thomasina, The Cat Who Thought She Was God" in the library of my parochial grade-school, almost 40 years ago. I imagine the deacons were utterly unaware of what a "subversive", shamanic book they were providing their 2nd-grade student!"
Oh, and the book ending? A bit of snark, not sugar. The veterinarian is now trying his best to suck up to the cat he hated before - and she's having none of it.