8yo: You know what I keep thinking about?
Me: What?
8yo: What if every time you blinked, you slipped into a different universe, but nothing about it was different? How would you know?
Me: ...
8yo: Every time I blink, I think about it.
Me: Well. What if that happens but the new universe IS different but in a way you couldn't possibly realise, like a person in China has a different name or some flower somewhere died or something like that?
8yo: ...
8yo: Thanks. Now I'm never going to stop thinking about THAT, either
Consider reading Soliton by @gregeganSF. It explores a similar world.
I actually meant Solidity (silly typos..), but you're right that Singleton is also related.