On a more serious note, I have absolutely no basis for this whatsoever but I think it's likely there's an antimatter universe somewhere, and that that and our universe spontaneously came into existence from nothing. 0 = -1 + 1. I mean, it's almost certainly nonsensical to the people who study this stuff but it's a fun idea
I don't know enough either, but a fun thought experiment is maybe we're the anituniverse? There's a lot more mass in the universe, than there should be, and we don't know what it is. It's just "dark matter" and "dark energy".
Edit: please correct me if I'm wrong, I've only read pop science stuff like Hawkins books
There is a theorie where we could live inside a blackhole, maybe it’s the creation of it that we call the bigbang and it somehow explain why the universe is in expansion.