Almost as long as superhero comics have been around, the comic book crossover has been a mainstay of the art form. Not to be outdone, the CW's Arrowverse has made the crossover a yearly event ever since season one of The Flash, which was the first time the fledgling shared TV universe had a second show to crossover with (the first being Arrow). Since then, the Arrowverse has grown to include Supergirl and Legends of Tomorrow, and their yearly crossovers have seen this multitude of heroes battling the immortal conqueror Vandal Savage, alien invaders, and dark, Nazi versions of themselves from another universe. This season, the Arrowverse has announced their most unusual crossover yet; Elseworlds.

Related: 10 Things We Want To See In Elseworlds (And 10 Things We Don't)

Little has been announced regarding the plot of this crossover, but Elseworlds refers to DC Comics stories that take place outside the regular DC Universe continuity, allowing writers to create stories that greatly alter the accepted history of the characters. So let's take a look at some of the things that we know we'll be seeing in this ambitious crossover event, and a few things on our wishlist.

10. Confirmed: Batwoman

For a while now, fans have wondered what role Batman plays in the Arrowverse. There have been teases, such as a character mentioning Gotham City on Supergirl, or Oliver Queen name-dropping Bruce Wayne at a press conference on Arrow, but never anything more concrete. In Elseworlds though, we're finally taking a trip to the Arrowverse Gotham City and meeting our first member of the Bat-family: Batwoman, played by Ruby Rose. In an interview with EW, Caroline Dries (a consultant on the crossover and EP for the potential Batwoman series) explained that Batman has been absent from Gotham for three years and the city is essentially falling apart.

9. Confirmed: John Wesley Shipp As Barry Allen

john wesley shipp original flash

One of the most surprising pictures to come from the set of the Elseworlds crossover was that of John Wesley Shipp dressed up in the original suit from his turn as the Scarlet Speedster in the short-lived '90s series The Flash. While there's no word on which specific speedster Shipp is playing under the mask (as he's played both Henry Allen and Jay Garrick in the Arrowverse), the last time he wore that particular costume he was portraying Barry Allen. So, since Elseworlds is wreaking complete havoc with reality in the Arrowverse, it's not too far outside the realm of possibilities for Shipp to reprise his role as an alternate version of Barry himself.

8. Confirmed: Evil Superman

Tyler Hoechlin made his debut as Superman in the season two premiere of Supergirl and will be returning to the Arrowverse in Elseworlds. What's interesting is that a tweet from Arrow star Stephen Amell showed Hoechlin dressed in a black version of the Superman suit. While switching to a black suit doesn't necessarily mean a turn to evil (it's comics though...that almost definitely means he's evil), in additional set photos and video this black-suited Superman can be seen threatening Flash's life, holding him hostage to Supergirl and the red and blue Superman. Considering the multiverse nature of Elseworlds, it may be that this black-suited Superman is an evil version of Kal-El from another reality.

7. Confirmed: The Monitor

Thanks again to EW, we got our first look at LaMonica Garrett as the cosmic DC character, The Monitor. Originally created by Marv Wolfman and George Perez for DC Comics in the 1980s, the Monitor is near omnipotent and was one of the main characters in the DC epic event Crisis on Infinite Earths. Wolfman has stated that he was extremely impressed with the Arrowverse depiction of the Monitor. While it's not completely clear what the Monitor's role will be in Elseworlds, in the image we can see that he appears to be holding the large book that black-suited Superman is reading from in some of the set photos that have shown up online. Also, it appears that the Monitor will be at least somewhat antagonistic, as Barry Allen/Flash star Grant Gustin described Garrett's performance to EW as "intimidating" and "a monster".

6. Confirmed: Lois Lane

The larger Superman family has been teased and talked about since season one of Supergirl. But in Elseworlds, we're finally going to see intrepid reporter and Superman's longtime love, Lois Lane (played by Elizabeth Tulloch). Season one of Supergirl featured Lois' sister Lucy Lane, and her father General Sam Lane, but this is the first time that Lois herself will be shown on screen. It's not yet known how much or little of Lois we'll be seeing in the crossover event, but a photo that Supergirl star Melissa Benoist posted to her Instagram shows herself, Tyler Hoechlin, and Tulloch on what appears to be a farm, which could mean that we'll see a visit to the famous Kent family farm in Smallville, Kansas.

5. Confirmed: Life Swapped Green Arrow And Flash

So here's where it really starts getting weird. In what appears to be the driving narrative force of Elseworlds, Barry Allen and Oliver Queen will be swapping lives, and they're the only people aware of the change. Queen will have super-speed and call himself the Flash, while Allen will be de-powered and protecting Star City as the vigilante Green Arrow. Amell shared the promo poster for Elseworlds via Twitter, showing the two heroes wearing swapped superhero costumes. According to EW, the reason reality is warped is due to a mad doctor at Arkham Asylum named Dr. John Deegan (Jeremy Davies), who has been playing with the fabric of reality.

4. Confirmed: Nora Fries

Another newcomer to the Arrowverse universe making her debut in Elseworlds is Nora Fries. Fans will remember that Nora Fries is the wife of Dr. Victor Fries, better known as the Batman villain Mr. Freeze. Nora will be played by Cassandra Jean Amell, who is the real world wife of Green Arrow himself, Stephen Amell. Victor Fries was name-dropped in a recent episode of The Flash, so the potential is there for a role for both Mr. and Mrs. Fries in the larger Arrowverse, but as of now, how much involvement Nora will have in the Elseworlds event is unclear.

3. Wishlist: Batman (Gotham By Gaslight)

batman saving a woman in gotham by gaslight

If we're making an Elseworlds wishlist, let's go big with it! In what is considered the original Elseworlds comic, Brian Augustyn and Hellboy creator Mike Mignola's Gotham By Gaslight told the story of a Victorian-era Batman hunting Jack The Ripper through the streets of Gotham City. It is a stunning, breathtaking vision of an alternate, low-tech, steampunk Batman that set the tone for all of the Elseworlds comics to follow. If the Arrowverse characters are going to be jumping from reality to reality and seeing alternate versions of each other, this is the version of Batman that would be most exciting.

2. Wishlist: Superman (Red Son)

Another landmark in the history of DC's "Elseworlds" comics was Superman: Red Son. Written by Kick-Ass creator Mark Millarthis three-part miniseries tells the tale of how the DC Universe would be different if baby Kal-El had landed in Soviet Ukraine in 1938 instead of Smallville, Kansas. He still grows up to be Superman, and is still a hero, but with a very different moral compass than the Man of Steel we all know. Superman: Red Son is truly one of the most thought-provoking Superman stories written in years and would make a fascinating addition to the Arrowverse. Also, considering that last year's Crisis on Earth-X crossover featured evil Nazi versions of Green Arrow and Supergirl, it would have been perfect to show Tyler Hoechlin's Superman leading the Soviet Union in an uneasy alliance with them.

1. Wishlist: Mr. Freeze

DC Comics Mr Freeze In His Laboratory

As stated, not only has the famous Batman villain Mr. Freeze been teased on The Flash, but his wife Nora will actually appear in Elseworlds. A genius scientist in the field of cryogenics, Dr. Victor Fries' wife Nora was stricken with an incurable disease and he chose to try and use cryogenics to keep her safe until a cure could be found. After an accident in his cryogenics lab, Victor was left unable to stand temperatures above freezing, leading him to build a special cryo-suit which kept him cold and augmented his strength. Along with a freeze gun, Victor set upon a life of crime as Mr. Freeze to continue funding his research into curing Nora, but also swore vengeance on the people who cursed him to a life in deep freeze. Adding Mr. Freeze to the Arrowverse, especially if treated with the gravity that he was given in Batman: The Animated Series, would be an immense treat for fans.

Next: DC Releases Extended Arrowverse Elseworlds Trailer

Elseworlds is a three-part event that will begin on Sunday, December 9th on The Flash at 8pm. Part two will be Monday, December 10th on Arrow at 8pm, and the conclusion will be Tuesday, December 11th on Supergirl, also at 8pm.