I was working as a librarian at a primary school when a class came in and watched this movie. I loved it, but I can’t remember much about it, and certainly not the title. Please help me find it?

Cartoon movie

Pre-2000

Had puppies, and maybe kittens

There were children helping them

It was quite dark in places, especially toward the end, and one of the animals might have got hurt or possibly almost died? But I’m fairly certain it did have a happy ending tho?

I’m fairly sure it wasn’t Pound Puppies, I don’t remember any of the animals wearing clothing?

Suggest anything, I really want to see this movie again, please?