What blew my mind is that it hasn't been proven that pi contains an infinte number of ones, for instance. It's not out of the question that there is a decimal place where the last 1 appears and there are none from then on.

It's not really likely, but we simply don't know and it is possible. It sounds weird given how many decimals of pi we've calculated, until you realise we've literally calculated 0% of them.

Whenever I think about the possibility of a Multiverse it just gets so unbelievably convoluted that I can't believe that that's how the Universe/Multiverse actually exists. Is the idea that every potential change in every atom or event in the Universe leads to all these other Universes, all co-existing, no matter how small & insignificant the differences? So we'd have a ridiculous number of Universes whose sole difference from ours is that a single atom behaved slightly differently in a rock out in the parking lot. Then multiply that by EVERY possible atom in the entire Universe, all behaving slightly differently.

That's just physical matter, what about conscious decisions made by living things? So in one Universe I filled my bowl of cereal with X oz of milk VS another universe where I filled it with X+1 oz of milk, and so on. All these micro-decisions that branch out into separate timelines, multiplied by the number of living entities in the Universe, every second of every day.

So are new Universes just constantly springing into existence at every moment in time, connected to every atom and every living thing, just brought about by tiny differences? I write some gobbledygook here: aksfhkashdf in one universe, adshfoasfdoajsidd in another, pooigjmasiodmfas in another, and so on. Multiple universes all suddenly springing into existence based on random key presses? Universes can't possibly be that "easy" to create can they, all that mass and energy, just poofed into existence, and it's constantly happening every second? Is mass, energy, and space just meaningless?

Or is it some other more basic set of differences describe the universe, just the starting conditions are different, but from there, each different Universe just proceeds as is, without multiple branching timelines? I'm not smart enough to understand any of it, it just quickly gets so incredibly convoluted and complicated for me to wrap my brain around.

CDs are optical storage, just plastic with tiny bumps. It's magnetic and solid state storage that can have bit flipping.

I think a lot of people assume a multiverse works that way because popular fiction makes it look like it does. However popular fiction is using something more akin to an omniverse (idk if there is an actual agreed scientific definition for a collection of multiple multiverses so Im just using that).

Using your analogy with the donkey kong discs being different universes with slight alterations in the warehouse (multiverse). In an omniverse scenario that you see in popular fiction, next door you'd have another warehouse but instead of donkey kong discs it is mario discs, or maybe donkey kong plushies.

However again that's all speculative of if there even is a multiverse let alone something larger than that

Natural numbers doesn't contain 2.5 because we define it so. Similarly all those CDs are practically the same because it's made in a factory designed to minimize the variance. Is there a similar strong will or intention in how a multiverse evolves?

due to the nature of infinity — a la monkeys and typewriters — you could have not only a single CD that due to a catastrophic series of errors is actually something completely different from a CD — but an infinite number of them.

Is it entirely beyond the realms of possibility that an infinitesimally small stroke of luck could create a sentient race of CD people? Except "small" doesn't make sense in infinity — "small" just means "a less common certainty"

Yeah, if there's a multiverse where all possibilities play out, and if any universe can directly affect another, then there's an infinite number of universes that do affect or get affected by others and there's an infinite number of universes that don't.

Just like time travel with multiple timelines. If you travel back in time, you're splitting off at least 3 timelines. One is the original where the past remains unchanged and you timetravel, one is the original where the past is the same and you fail to timetravel, and one is the original timeline up to the point that you travel to, at which point it diverges probably very drastically (which makes me think that traveling back in time will be a one way trip because your original timeline won't be very close to the new one's future). Though if you can travel back to the future, there will be one version where you never do to pair with the one where you do.

Though I'm not holding my breath on any kind of direct influence between universe and timelines other than maybe something like gravity from one can affect others, and really don't think that traveling from one to another will be possible. But who knows what is really possible, as advanced as we might be compared to our past, I wouldn't be surprised if our knowledge is still just a drop out of a whole ocean.

would humans even evolve? Would life even evolve?

Such movies generally explain it as there are other universes locally clustered to yours. As in, there are so many universes that some are only a few decisions/variables off yours

You are correct in thinking that there would be an infinite subset of universes where humans never evolved. However, there would also be a much smaller, but still infinite, subset of universes where humans did evolve. And there would be a muuuuuch smaller, but still infinite, subset of universes where the history of the universe and all of human history transpired exactly as it did in our universe, up until the point it diverged with the necessary changes in order to be relevant to the plot of the movie. That tiny tiny tiny subset is the only thing we talk about in movies, because otherwise it would be too confusing for general audiences. Hope this helps.

One small change can lead to a totally divergent path. Think about it this way. You are supposed to meet your SO today at work. But you forgot to brush. No big deal. Right? Well your SO says hello, so you say it back and then she gets a whiff. Well end of conversation and that’s that. No wife. No kids. Not with her.

Or maybe you miss that buss that you barely caught. Or maybe you win the lotto at 19 and that changes everything for you.

You’re thinking wrong if you think lives have to be drastically different in every way for it to manifest as a whole new life. It can be the smallest thing but that tiny, infinitesimal thing can lead to a cascade of change or shunt people down an entirely different path.

Lastly, your ancestors would also be subject to these events, making all their lives very different as well.

Butterfly Effect.

There could be different laws of physics in this universe that makes it near impossible for somebody outside of it to visit. Or, from another perspective, would you wilingly visit yourself?