Elseworlds: Here Is Everything We Know About the Arrowverse Crossover So Far

The Arrowverse crossover has become a staple of The CW's DCTV series. It all began in 2013, when a not yet superpowered Barry Allen was introduced in a two-part Arrow episode, and since then, the crossovers have been cemented as an annual tradition.

The following year saw the first official team-up between Oliver and Barry as the full-fledged superhero The Flash in "The Brave and the Bold." Then we had a massive lead-in to the Legends of Tomorrow with "Legends of Yesterday" in 2015, a proper alien invasion with 2016's "Invasion!," and the biggest superhero extravaganza so far with last year's "Crisis on Earth-X." Now, the Arrowverse is set to offer fans its most ambitious crossover yet with "Elseworlds."

For the past few weeks, the various stars from the Arrowverse superhero shows have been filming the crossover, and as we've seen time and again, when shows are filming, cameras are snapping photos. From new costumes to new identities and even a few new locales, here's a roundup of everything we know about the Arrowverse's "Elseworlds" event -- so far.

Batwoman, Gotham City... and Arkham Asylum?

Before we even knew the title of the crossover, it was revealed was that a member of the Bat-family would finally appear in the Arrowverse: Kate Kane, aka Batwoman, with John Wick: Chapter 2 actress Ruby Rose eventually cast in the role. Though Batman himself wouldn't appear in the event, Batwoman will debut in all her glory with a costume torn straight from the comics.

Whenever a member of the Bat-family is involved, Gotham City can't be far behind, and that's the case here, in a big way. While Gotham has been mentioned previously in the Arrowverse, the crossover will mark the first time that we actually pay a visit to the legendary city. What's more, we also know that the infamous Arkham Asylum will also feature in "Elseworlds," given that Lost actor Jeremy Davis has been cast in the role of Arkham doctor John Deegan.

Kate Kane and John Deegan won't be the only Gotham denizens we see in the crossover. Stephen Amell's wife Cassandra Jean Amell will also appear i the crossover as Nora Fries, the wife of iconic Batman villain Mr. Freeze. What hasn't been confirmed yet is whether we'll see the ice-cold villain himself.

Lois & Clark

In the past four crossovers, we've seen Green Arrow and The Flash team up with the likes of Supergirl, the Ray, and the entire Legends of Tomorrow team, but "Elseworlds" will mark the first time that Barry Allen and Oliver Queen cross paths with Superman. Tyler Hoechlin, who has made sporadic appearances as the Last Son of Krypton on Supergirl, will not only take part in the crossover, he will appear in all three of its episodes. What's more, Clark Kent won't arrive alone -- his better half, Lois Lane, will also feature in the storyline, where she will be played by former Grimm star Elizabeth Tulloch.

Not only will we see Superman and Supergirl fight side-by-side once more, "Elseworlds" will debut the Arrowverse's version of Superman's fan-favorite black costume. We don't yet know the circumstances surrounding the costume change, but it's a safe bet we'll be looking at an alternate universe take on the Man of Steel -- a reality one where Superman isn't the only hero who's different.

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Alternate Versions of Barry Allen and Oliver Queen

Perhaps the biggest question regarding "Elseworlds" is what's going on with Barry Allen and Oliver Queen. First, the two characters were spotted on set alongside Tyler Hoechlin's black suit-wearing Superman, where they appeared to be members of a biker bang. The mystery deepened when the biker costumes fully debuted, revealing that the two are actually a duo nicknamed the Trigger Twins, a nod to either a criminal duo from the comic books, or the original Trigger Twins, a pair of heroes from DC's Silver Age Western comics.

But that's not all; the first official "Elseworlds" poster teases a swap where Barry Allen and Oliver Queen have traded superhero identities, with Allen now the Emerald Archer, and Queen the Scarlet Speedster.

We don't have a lot of answers about either version of the two leads, but given that the crossover is titled "Elseworlds," it's likely that we will see more than one alternate Earth when the superheroes team up and take on the different identities. Whether other heroes will join in on the identity switches has yet to be revealed.

A Trip to Smallville

There are many iconic locations in the world of DC, and we are bound to see many of them in "Elseworlds." Outside of Star City, Central City, Gotham and Arkham Asylum, it's also been confirmed that the event will feature Clark Kent's homestead in Smallville, KA. In fact, Melissa Benoist, Stephen Amell and Grant Gustin were all spotted on the Kent farm set, as well as Tyler Hoechlin and Elizabeth Tulloch.

To make tings even more meta, the Kent farm that will be seen in the crossover is actually the same one that was used in the Superman origin television show, Smallville.

Enter the Monitor

If Green Arrow, The Flash, Supergirl, Lois Lane, Superman and Batwoman weren't enough, we've also had confirmation that another important DC Comics character will also appear in the upcoming crossover: the Monitor, who will be played by LaMonica Garrett. A powerful member of an alien race who watches over the multiverse, the Monitor has featured in such classic DC stories as Crisis on Infinite Earths.

We don't yet know what role the Monitor will play in the event, but with a title that calls back to all the alternate universe stories in the DC library, it's a no-brainer that "Elseworlds" will take us on a trip through the DC Multiverse. How all the pieces will fit together remains to be seen, and we simply can't wait to find out.

The highly-anticipated “Elseworlds” crossover will air over three nights, starting Sunday December 9 to Tuesday, December 11.