8 Highlights as 'Elseworlds' Crossover Invades 'Arrow': Batwoman, Green Lantern, Batman and More

The CW is going all out in their latest crossover event, and it looks like "Elseworlds" might just be a harbinger -- pun intended -- of even worse to come.

On Monday night, the action shifted over to "Arrow" and brought along even more DC Easter eggs than the "Flash" premiere Sunday night. Not only did we get the long-awaited and highly-anticipated debut of Ruby Rose as Batwoman, but we finally learned how Oliver and Barry pulled a "Freaky Friday" (or is that "Quantum Leap"?) and why the Monitor is mucking with reality like this.

On top of that, we got the return of Earth-90 Flash, a Green Lantern hint, and more nods to the Batman mythology that you can shake Mr. Freeze's cold gun at. Seriously it was all we could do to keep track of it all as our intrepid trinity of heroes made their way through Arkham.

We've gathered all the highlights, Easter eggs and revelations that are still blowing our minds below ... and there's still one night left to go in this madness:

For years, fans have wondered if Green Arrow was the CW's analog for Batman, as they weren't allowed to use the prestige DC property, but with the recent inclusion of Superman into their multiverse, it seems the powers-that-be have relaxed their stance on this. Now, we get our most direct acknowledgement yet that Batman exists in this universe.

However, this is the version of Batman that is more of an urban myth than an established superhero. And on top of that, we find out that he's been missing for about three years, along with Bruce Wayne. The comics have removed Batman from Gotham for various reasons over the years, but it remains to be seen what the thought is here.

One of the throwaway lines savvy viewers picked up on was when the Earth-90 version of the Flash actually recognized John Diggle. What's more he asked him why he wasn't wearing his ring, which would appear to be a clear nod to the Green Lantern mythology and the fact that John Diggle is so very much like John Stewart, who is one of Earth's Green Lanterns.

It's already been established that Earth-90 Flash is part of the Justice League of America on his world, which means he's fought side by side with the Green Lantern. Just as Batman has been a part of Earth-1 all this time, it's safe to presume that the Green Lantern Corps is out there policing the universe; we just haven't met them yet.

Well, this is our first clear indication that there may be a connection between Diggle and the Corps. Could it be a hint that he'll become a Green Lantern in the future? With his military background, discipline and training, Diggle is already exactly who Stewart was before he was selected. So was this just an Easter egg, or a hint of exciting things to come?

In his absence, his cousin stepped up as Batwoman, taking the city under her wing and even hijacking the Wayne Enterprises building. It also looks like she may have taken over the Batcave, but it wasn't completely clear what the case was there. As this episode also served as a sort of backdoor pilot for a possible "Batwoman" series, it's worth unpacking her world.

With Batman gone, Gotham has grown even darker, and it appears that Batwoman is working alone. Nevertheless, she mentions at least one R&D guy, which could be her gadget-maker a la Lucius Fox for Batman. She's got a Batmobile, all of Batman's cool gadgets and more tattoos than Kara could see with her x-ray vision.

Rose played it a little too gruff -- especially when walking through the Batcave(?) -- but there's potential for her to find a compelling take on the character. Plus, the mystery of what's happened to Bruce and Gotham in his absence would make a great opening arc. With "Gotham" wrapping this year, DC may be planning a quick return to Gotham with a new Bat-lead and we're here for it.

Plus, with "Arrow" getting long in the tooth, should they decide to retire that show, the DCW Universe can continue with a new grim-and-gritty character who's already sparked up some chemistry with her classic gender-swapped counterpart, Supergirl. They already payed tribute to the classic moniker for the pairing of their male counterparts when Batwoman suggested they could have been the "World's Finest."

Speaking of Supergirl, we've long suspected that her Earth has a Batman of its own, and now we get that confirmed. Even further, Kara told Batwoman that Batman and her Superman are close friends. Considering Earth-38 is closer to a Silver Age reality, with a little more light and optimism infused into its DNA than Earth-1, it's easy to imagine that friendship.

Should "Batwoman" go to series, future crossovers could eventually introduce this version of Batman, adding to the complexity of Batwoman's relationship with her cousin, and perhaps aiding in the mystery of where he's gone. After all, it's usually pretty out of character for Bruce to abandon Gotham, considering his obsessive drive to "save" it.

One of the reasons we love Batman so much is his incredible rogues gallery of villains, and we got hints at so many of them in this episode. We also got the suggestion that most of them are behind bars at Arkham Asylum, including Oswald Cobblepot (Penguin), Edward Nigma (Riddler), Pamela Isley (Poison Ivy), Basil Karlo (Clayface) and even the episode's writer, Marc Guggenheim.

The most prominently featured villain was Nora Fries, wife to classic villain Mr. Freeze. In this continuity, though, it appears that she might suffer the same influction as her husband, as she was lamenting that she needs to keep her body temperature below freezing to survive.

In comics and "Batman: The Animated Series" continuity, it's Victor Fries who suffers this infliction. His wife, Nora, is kept frozen to keep her in a form of stasis as she's suffering a terminal ailment. Everything Victor does is toward the pursuit of finding a cure for her. It remains to be seen if this Mrs. Freeze's husband is the one dying, or if she's just a gender-bent take on the character.

And then there's the spilled chemical compound labeled under the name J.Crane, an obvious nod to Jonathan Crane AKA the Scarecrow and his fear toxin, which explains why Oliver and Barry were fighting their arch-foes ... though it doesn't exactly make sense -- considering their minds are swapped -- that they would fight one another's arch-foes. But hey, just roll with it.

No matter how you shake it, though, the villains make Batman, have made "Gotham," and could easily make "Batwoman" a show to watch. Maybe the brief prison break could be the catalyst that launches her series proper, as it certainly seems like almost all of the big ones are currently locked up.

But Batman's legacy was all over this episode in so many different ways, some more subtle than a roster of his greatest villains. When Kara dropped by to visit Kate Kane (Batwoman) in Bruce's old office that she's occupied, Kara noticed a bust of Shakespeare in a box.

This was the infamous bust the dynamic duo of the 1960s "Batman" series used to open the entrance to their Batcave. Then, there's the shape of the Bat-logo on the spotlight atop the GCPD building, shaped like the logo used in Christopher Nolan's "Dark Knight" series of films.

And then, continuing a long-standing trend of giving shoutouts to past creators, one of the big fights of this episode took place on the corner of Nolan and Burton, a nod to Tim Burton's 1989 "Batman" series of films. Of course, with Barry Allen from the 1990's "Flash" series showing up, maybe all these different versions of Batman exist out there on other worlds.

The episode ended with another reality shift, dropping Oliver and Barry into the identities of the Trigger Twins, a pair of lookalike bank robbers. This means neither of them have super-speed, nor Arrow's meticulous training. They are, however, apparently good with guns.

Not that this will do much good when Superman drops in wearing a black suit. Sure, he looks like Kara's Superman from Earth-39, but there's a new menace to him and (SPOILER WARNING) the teaser for Tuesday night's conclusion hints that this Superman has perhaps positioned himself as the law in this world.

There's a history of black Superman suits in the comics, most prominently when Superman wore on as part of his recovery after his death at the hands of Doomsday. And then there's the Superboy-Prime character (don't even ask his backstory) who wore one and was more than a little unhinged.

In this case, it looks like this version of Superman may be Dr. Destiny nee Deegan, who was urged to "think bigger" when the Monitor gave the Book of Destiny back to him. Could he have positioned himself as the world's most powerful superhero and rule the world?

There's certainly precedent for this as well, most recently in the "Injustice" series of video games and comic books. Superman as despot is very difficult and dangerous to take down on a good day, which could explain why he depowered Barry and Oliver. As for Supergirl, it remains to be seen what happened to her as she just disappeared.

The biggest and most exciting reveal of the episode, though, came when the Monitor revealed that all of this is just a proving ground, a way for him to test parallel worlds in an attempt to find one worthy of taking on a threat bigger than him in the coming "crisis."

Well, that can only be the "Crisis on Infinite Earths," a multiverse-shattering event that wiped out the DC multiverse for a while, leaving only one surviving universe. In that story, the Monitor assembled heroes from a selection of surviving worlds to face the threat of the Anti-Monitor, his evil counterpart.

The coming of this crisis was preceded by red skies and storms, as have been following Barry and Oliver around Earth-1, and as appeared to have enveloped Earth-90 before that Flash escaped. Whether that's the big crossover for next season or something further down the road this season, there is no bigger story in the entire DC Universe than the original "Crisis," so that one could break the DCW Universe as we know it forever.

"Elseworlds" concludes Tuesday night on "Supergirl" at 8 p.m. ET on The CW.

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