"Elseworlds": First Look at the Arrowverse's Arkham Asylum

The upcoming "Elseworlds" crossover is expected to change the Arrowverse as we know it -- including bringing in a familiar locale.

The newest promo for the upcoming three-night event, which served as the first official footage of Ruby Rose's Batwoman, briefly featured a sequence establishing the Arrowverse's Gotham City. At one point in the trailer, which you can check a screenshot of below, several jumpsuit-wearing inmates (including one who looks like, but probably isn't, the Joker) can be seen escaping from Arkham Asylum.

Granted, Arrowverse fans already had an idea of Arkham Asylum's role in the crossover, with Dr. John Deegan (Jeremy Davies) serving as the instigator for the whole event. (An official photo released earlier today also showed Deegan inside what appeared to be Arkham.) But still, seeing the outside of the iconic building is sure to be a delight to some, especially considering the Arrowverse's history with mentioning that part of the DC universe.

The three-night event will see Oliver Queen (Stephen Amell) and Barry Allen (Grant Gustin) accidentally switching lives when Deegan rewrites reality, forcing Kara Danvers (Melissa Benoist) to help intervene.

"My initial reaction in reading the scripts this year was that it would be a hoot to film." Benoist explained in a recent interview. "The comedy just lives in this. Even just seeing them in each other's suits is funny; they're literally putting themselves in each other's shoes! ...[Kara] inevitably becomes kind of a middleman because ultimately there's conflict between the two and they start butting heads."

"She's trying to help them navigate what they're going through and support them and kind of battle their way back to being who they're supposed to be," Supergirl EP Robert Rovner added.

"The most fun aspect about really focusing on the leads is we really had a chance to tell a story about the troika that we've never really been able to do before," Arrow consulting producer Marc Guggenheim explained. "When you have Legends of Tomorrow part of it, and all of the other secondary and supporting characters, the amount of time we had Grant and Stephen and Melissa on screen together was actually pretty minimal in other crossovers compared to this year."

The three-night "Elseworlds" event will begin with The Flash on Sunday, December 9th, before carrying over to December 10th's Arrow and December 11's Supergirl.