I read this one in a short story collection in the late 1970s or early 1980s. Definitely before 1985.
A (orphaned?) boy and his pet cat are sent to live with his aunt, uncle and cousin. The cousin is a vicious bully. Eventually the cat leads the boy to a book on (Egyptian?) mythology or spell book of some kind. Somehow the boy convinces the cousin to play a game with him, which is actually a cover for invoking a spell that causes the cat and cousin to switch bodies.
In the epilogue, the aunt is commenting on how pleased she is her son (the bullying cousin) really changed his demeanor after her nephew’s cat got distemper and had to be put down. She’s happy that now the two boys are the best of friends.
A few more details popped into my head. I believe the title of the story was simply the cat’s name, which for some reason I think started with ‘B’. Hopefully I’m not conflating it with something else.
That’s not it, but I think you may have led me to it.
I found an online copy of Spacetime for Springers. While reading it, three thoughts popped into my head. (1) I’ve read this story before and (2) it was in the same compilation as my OP story, and (3) the collection was an anthology of cat stories.
So I checked isfdb.org to see what collections contain the Leiber story, and immediately recognized the cover of Supernatural Cats. I checked the contents list and foundBalu by August Derleth matched my “cat name starting with B” recollection. Further searching found this synopsis:
[QUOTE=Publisher’s Weekly]
In August Derleth’s “Balu,” an orphaned boy and his cat settle their score with Cousin Harold in a delightfully grotesque manner.
[/QUOTE]
So it sure sounds like my story. I’m going to check the library this weekend to try to confirm it.
The story ends a bit more casually racist than you might remember:
[Quote=August Derleth]
You will be delighted to learn that the boys, who were Once so quarrelsome, get along beautifully together now. It is so inspiring to witness such a transformation. Harold, who had not been kind to Walter, I must admit, now seems actually to fawn upon him—not disgustingly, of course; but certainly he is extremely fond of his cousin. And Walter, now that we have had to dispose of his cat, (which’ apparently went into fits one day in his room and could not be brought put of them), has the somewhat quaint habit of calling Harold Balu, after his cat. Oddly enough the servants, who once adored Harold, now. seem to be unable to tolerate his presence. But, I suppose, one must, expect blacks to be a little queer…
[/QUOTE]
Looking more at the story, it has not, um, aged favorably:
*HAROLD’S second attack came within the week. He came complaining that the servants were frightened of Balu. There were but two, both black. It was true that the blacks were frightened of Balu; they had always been. Walter remembered very well an old Negro who had worked for a while for his father. He had shunned the cat; more than that, he had walked carefully all around it. In this house, it was worse because the blacks were women. Women always carried on so. He had heard them.
He had heard them say, "Lawdy, dat cat am a witch-cat, hope to die!” He had heard them say, "Dat Balu got de sperit in him way down deep. He old. He old es de world.”*
Read it when I got home (archive.org is blocked at work*) and can confirm that it is the story I was thinking of. Yeah, I didn’t remember the casual racism or sexism. Or maybe my insensitive teenage self didn’t pick up on it.
*Good thing, since I now know there are back issues of Weird Tales online. I had a few collections in high school and loved them. They were my first exposure to Lovecraft.