In thinking about how Stephen King likes to rewrite stories, I think the origins for Sleepwalkers can be partially traced the the 1985 anthology film Cat's Eye, also based on King's short stories. In particular, the 3rd story is called "The General" and is about a cat who must protect a small girl from a troll that is trying to steal her breath (life-force?) and kill her.
I remember watching this as a kid and it immediately came to mind listening to the episode this week.