Comment 39 by KenChimp :

Exactly. Which is why we do not see alive/dead cats, people, places and things popping into and out of existence around us in the world above the nano level. It isn't that such events are impossible, rather that they are so extremely improbable due to what you've just stated that we may as well not consider them as realistic events.

If we have a real cat in a box, the box and everything in it would interact with the world around it, through gravity and so on. So if an interaction takes place in the box, it would interact with a system that interacts with everything else.

So in that respect, it's a problematic anology for something that happens among elementary particles, such as a photon going through a double-slit. But perhaps a little modification:

But if the box and the cat existed in a place where interaction with the rest of the universe was negligeble or non-existent (such a universe of its own), would then perhaps the whole system, from our perspective, be in a state that would not collapse until something from this universe interacted with it?

Perhaps it only needs to be negligeble and not non-existent? There could be some kind of quantum limit (connected to the uncertainty principle?) An electron has mass, but I think it also shows the typical interference pattern when it goes through a double-slit. Gravity does not seem to interact enough with the wave to collapse the wave function.