They meet again! The Flash supplies Part Three with John Wesley Shipp—who was The Flash in CBS’s iteration years before he played Barry’s father Henry on the CW—back in his scarlet ensemble to help the cause alongside Grant Gustin’s current Flash. We learned that Shipp’s Speedster was from Earth-90 during last year’s Elseworld’s crossover.

Batwoman ‘s installment also introduces us to Kevin Conroy’s Bruce Wayne, who may or may not be the cousin she has taken over for. If he is from her Earth, he has some explaining to do. If he’s from one of the other Earths…well, he still has some explaining to do! Like, what is with the exo-skeleton? And why does that Batsuit look so different?

Don’t answer that, because two of those other Supermen are already having issues on Batwoman . Brandon Routh (who also plays Legends ‘ Ray) is back in the cape as a Man of Steel inspired by the comic book Kingdom Come and definitely not OK with Tyler’s Kal-El from Earth-38. Maybe it has something to do with that Daily Planet headline in the back?

“So…on other Earths, there are other Lois and Clarks? Are they as cute as us?”

Smallville ‘s Clark Kent (Tom Welling) shows up on Batwoman for the second part and it remains to be seen which Earth he is from. But we do know that whichever one it is…

More suits show up on Supergirl ‘s episode, including Ray (Brandon Routh) as the Atom and Batwoman (Ruby Rose). All from Earth-1, although Mia is from the future, so she has that going on.

The madness kicks off in Supergirl , with Lois (Elizabeth Tulloch) and Superman (Tyler Hoechlin) coming from Krypton to Earth-1 after Lyla (Audrey Marie Anderson)—who has been somehow turned into the Monitor’s emissary, Harbinger—begins gathering heroes like Oliver (Stephen Amell) and Mia (Katherine McNamara) to fight against the Anti-Monitor.

We're less than a week away from worlds colliding (and collapsing) as the Arrowverse mounts its annual crossover extravaganza and this year, it's beyond big. We're talking monolithic. Unimaginably epic. More than TV is used to delivering. And, let's face it, Crisis on Infinite Earths may also be causing a slight crisis among fans or newbies who aren't exactly well-versed in whatever the hell "Infinite Earths" even means. So we're here for you as much as we're here for it.

So, imagine that the Arrowverse is TV. Each network is its own universe, with shows about heroes and villains that are at the same time familiar and different, depending on which network they were on. So Earth-HBO could have an Arrow, but it would be big- budget Emmy bait about Oliver (Stephen Amell) battling dragons, Meryl Streep, and unrealistic series-finale expectations. Earth-Bravo's Supergirl would be a Real Housewives of National City with tons of bitchy confessional clips of Lena (Katie McGrath) shading Kara (Melissa Benoist), and Lex Luthor (Jon Cryer) hosting cast reunion specials.

On Earth-NBC, Legends of Tomorrow would be a single-camera workplace comedy about the superhero-headquarters support staff led by Sara (Caity Lotz) and her lovelorn tech-nerd colleague, Ray (Brandon Routh). Batwoman would be known as The B Word on Earth-Showtime. And Earth-Fox would probably just cancel Black Lightning after a season, but their foul-mouthed animated hit, The Flash-er, would run (get it) forever.

In many ways, the Multiverse is very much the same concept as previous shows that have dealt with alt-worlds like Fringe, The Man in the High Castle, Sliders, Timeless, and Counterpart. Or Canada... things look just like they do in America but there is a totally unique vibe happening up there.

When DC Comics first unleashed Crisis on Infinite Earths, it was in the form of a wildly popular 12-issue miniseries that ran from 1985 to 1986. Written by Marv Wolfman and drawn by George Perez, Crisis was designed to streamline the then-unwieldy DC continuity, which at the time was a mess of various timelines, backstories and settings. As it states in the opening pages, "In the beginning, there was only one. A single black infinitude."

Then, as time went on, a small light grew into an explosive Big Bang-ish event and "in that instant, a multiverse was born. A Multiverse of worlds vibrating and replicating...[what] should have been one became many." The story saw an interstellar being known as The Monitor calling on superheroes from each of the DC Comics "Earths" to battle the Anti-Monitor, his evil counterpart who was set on destroying all of their realities. And in the ensuing war, worlds indeed were lost, as were certain versions of characters who existed on those destroyed Earths.

The same is most likely set to happen on TV's Crisis, especially since The Monitor (LaMonica Garrett) has already informed Oliver and Barry (Grant Gustin) that they have to die for worlds to live. This was also teased back in The Flash pilot when Barry saw the future headline that he vanished "in a Crisis." Since then, we have learned of several Arrowverse Earths — Arrow, The Flash, Batwoman and presumably Black Lightning all take place on Earth-1, but Supergirl takes place on the Earth-38 where Superman (Tyler Hoechlin) and Lois Lane (Elizabeth Tulloch) also reside.

Katie Cassidy's Black Siren from Arrow and The Flash's Zoom (Teddy Sears) both came from Earth-2 (rest in peace); John Wesley Ship's version of Barry Allen from CBS's 1990 take on The Flash came from, fittingly, Earth-90 to appear in last year's Elseworlds crossover, while his retired speedster Jay Garrick was an Earth-3 visitor; Legends of Tomorrow has jumped around different Earths because that's their thing; and two years ago, the Crisis On Earth-X crossover introduced us to The Ray (Russell Tovey), a freedom fighter from a universe where villainous editions of our heroes worked with Nazis.

Each Earth's history and progress has been impacted by variations, some huge (like Germany winning WWII), others seemingly harmless. Some have doppelgängers of certain characters, others have older or angrier versions of them and still others are absolutely clueless about what is going on and who any of these heroes are.

More Earths will surely be revealed during Crisis, given that they are bringing in so many characters who can't all exist in the already-established universes. Since Hoechlin and Tulloch's Super-couple are the reps from Earth-38, it stands to reason that Tom Welling's Clark Kent and Erica Durance's Lois from Smallville will come from another reality. Maybe Earth-WB? Ashley Scott is set to resurrect her role as Huntress from the former network's Birds of Prey, so we'd allow the in-joke.

The duplicate Kal-Els also means the older Superman inspired by the Kingdom Come comic books and being played by Brandon Routh would have to hail from yet another Earth. Burt Ward, who played Robin in the classic Batman series, signed on as well and it would be perfect if he was from Earth-66. And what if the producers have more surprise guests on tap from DC Comics' other on-screen properties? Well, then we could soon be learning that the folks from Lucifer, Titans, Teen Titans, Stargirl, Doom Patrol, Gotham, Pennyworth, Young Justice, Human Target, the original Wonder Woman, even Watchmen, are each from their own Earth within the Multiverse.

We know, it's a lot. This business of the Multiverse can be trippy, trying to make sense of all the Earths and who came from where, but fear not. Like the comic-book Crisis, this one may actually help declutter the Arrowverse and bring the shows currently airing into one common continuity. Because the only thing cooler than bringing together so many TV heroes, old, new, animated and maybe even streaming, is the idea that they are just like the fans of their shows: Even though they all live in the same world, it's their differences that make them super.

Now, click through the gallery for some more explanations...and EXCLUSIVE FIRST LOOK IMAGES from the groundbreaking five-parter!