There's a theory that says we are living in a simulation, a simple explanation can be found here.
So what if this simulation is based on blockchain just like cryptocurrencies and indeed a parallel universe is just a fork like Ethereum and Ethereum Classic, and you can fork the current universe at any moment.
Also dreams can be sidechains so they don't need to follow the same physical rules but they are related to the main chain.
Of course this is absurd but possible so I feel a need for sharing this. See you, I'm going to my sidechain!