So, cats/animals in general dying on the set of Koneko Monogatari (released in the US as The Adventures of Milo and Otis) is 100% urban legend. It's bullshit they read elsewhere of "my uncle works at Nintendo" tier bullshit. No joke, the source(s) is a "my uncle/father/whoever works/lives in Japan and there was controversy at the time of release but I totally can't show you the original material because it's in Japanese!" post.
I have never been able to find the actual source to the claim, however I believe it came from a "behind the scenes" featurette someone uploaded to YouTube. It showed a pet crate with a bunch of adorable orange kittens in it and the explanation about how the director used many different animals based on their personality for whatever scenes they were filming that day. I think this, that they needed 40+ kittens (because of their personalities and ages) over the span of four years of filming mutated into 40+ kittens dying instead.
I know this is 🕰 but I did want to expound a bit on the
animal abuse rumors for Milo and Otis. The rumors were started by an Australian group called Animal Liberation Queensland, and while I can't say for sure if they're PETA level nutbars or a more legitimate group, by their own admission they had no solid evidence of animal abuse, just unsourced rumors and "concerns" that they got from literally just watching the movie. Their allegations were reported and magnified in a fucking tabloid paper, with about the level of restraint you'd expect from a tabloid, and that's when the rumors really started spreading and getting exaggerated like wildfire.
The American Humane Society did an investigation and found no proof of animal abuse, and several Japanese Humane Societies vouched that no animals were harmed in the making of the film.
At the risk of sounding like an SJW myself (sometimes turnabout is fair play), I'm relatively positive the persistence of rumors that cats and dogs were being used up like Kleenex on the set of Milo and Otis, and the credulity these stories are met with, relates very heavily to it being a Japanese film that gained worldwide mainstream recognition during an era when Japanese cinema was still extremely niche outside of Japan. After all, who knew if those backwards slanty eyed island dwellers had any concept of animal rights in the 80's. Don't they eat dogs over there or something?
If this were a film that was made in Nigeria or something and was important to that country's film legacy, the narrative of people like Dobson and the Tumblr crowd would be all about how these unjust rumors were a result of racism (with plenty of "wypipo bad" sperging), but since the Japanese rank so low on the progressive stack, none of them give a fuck and can't be bothered to get the facts straight.