Science

I see a video of that and the monkey's arms are partially restricted and still moving (and another where it says reenactment at the start)

I seem to remember a video where it peeled a banana using both an artificial and its own hand at the same time... and also solved a "touch points on the screen" test... but it's been some time ago, so maybe I'm hallucinating it 🤷

multiple brains (in the sense of multiple people) residing in the same body. Usage shifts (to allow rest)

Like what dolphins do, about sleeping with only one hemisphere at a time? I always wondered whether it causes dolphins to have split personalities, or something; supposedly sleep is needed for integrating experiences, so both hemispheres could be integrate some shared, but other exclusive experiences separately.

Or maybe they "daydream", with the awake hemisphere receiving the dreams of the sleeping one, so it can integrate them when it goes to sleep. Would be interesting to learn more about that... also from an AI training integration point of view.

backup/advice/talking

There... might... be a built-in mechanism in all human brains to do just that. Check out the "Third Man Syndrome", and the related "God Helmet" experiment:

https://en.m.wikipedia.org/wiki/Third_man_factor

https://en.m.wikipedia.org/wiki/God_helmet