Theoretically, parallel universes are nearly identical, but not exactly. There may be a parallel universes where Pres. John F. Kennedy was never assassinated, or where astronauts never landed on the Moon, or where the USSR never broke up into separate states, or where Hitler failed to slaughter several million Jews, or where Europeans never ventured to the New World and left the natives to live and develop on their own, and so forth.
Parallel universe explains an infinite amount of possibilities, and perhaps they are merely actually “parallel potentialities” that could have existed, but never fully manifested. Perhaps there is only one primary universe, where only a certain agenda will manifest, and perhaps certain potentialities or parallel universes could not fully manifest because certain events never took place in the primary universe. So a potential parallel universe might never become a primary universe, whereas a different parallel universe whose momentum has built up will indeed become the main universe. All such manifestations of such events that entered the primary universe were based on choices people made, and the momentum that was built up behind their choices.
Granted, this is a very limiting theory involving parallel universes, perhaps less dramatic. However, the idea of the Multiverse is more radical, as it involves the existence of countless parallel universes existing simultaneously, which means all of these potentialities exist at once, because all possible choices manifested in some form or another, hence creating these parallel universes, which would explain the bleeding through or reality shifts. This is very much like the many branches of a tree. Perhaps at one time there was only one universe; however, based on the definite choices people made throughout history, other universes were created, or perhaps you could call them separate timelines. In which case, there could be an infinite amount of timelines throughout the totality of existence. This would become the Multiverse.
And this is quite possibly why we experience these bleed-through phenomena, or reality shifts. Because certain incidents from a parallel universe will bleed through into ours momentarily, often causing confusion or disorientation. Is this why we have missing socks when we do laundry? Is this why the car keys you set on the coffee table strangely reappear inside the refrigerator? Or perhaps this is why the car that was tailgating you one second strangely disappears the next. Or perhaps you met someone and got to know him for a few months, and when you parted, then met again a few years later, he had absolutely no recollection of who you were. Or perhaps you heard about a famous individual’s death in the news, but then a year or two later you hear a news story discussing some event about the same person, implying he was still alive. There are numerous inconsistencies like this that we can cite, and the best explanation is the existence of parallel universes. However, it could be explained as somebody experiencing memory loss, or even some kind of fractured memory disorder, if not insanity. But that would mean a lot of people in this world are insane. Perhaps that is the case. Or perhaps we just can’t trust our own minds, which tend to play tricks on us. Or perhaps the existence of parallel universes is real.
And if so, does that mean each one of us has other selves? Is it possible that each individual has a countless number of other selves existing in these parallel universes? Something to think about.