This year's Arrowverse crossover, which will introduce Batwoman and bring together the heroes of Arrow, The Flash, and Supergirl, will be titled "Elseworlds," DC has confirmed.

Elseworlds was the name of an imprint that ran from 1989 until 2010, bringing new twists to familiar DC characters and presenting them in "what if..." scenarios.

When 52 reinstated DC's multiverse, which had been eliminated at the end of Crisis on Infinite Earths in the '80s, most of the popular Elseworlds stories were retroactively transformed into alternate Earths in DC's multiverse.

The crossover will feature Ruby Rose as Batwoman and Elizabeth Tulloch as Lois Lane, making her Arrowverse debut. Tyler Hoechlin will return as Superman.

While "Elseworlds" is likely just a clever title for the crossover, its use opens up a number of interesting possibilities. One scenario could be that Batman, whose existence has been implied but never directly stated on the Arrowverse shows, could be somehow replaced by or transformed into Batwoman. This would give a plausible explanation for the lack of Batman in the Arrowverse despite a story that will head to Gotham and feature Bat-concepts like Mister Freeze and Arkham Asylum.

One of the most popular Elseworlds series, 2003's Superman: Red Son, is providing some of the story for the upcoming season of Supergirl. There is no indication that the Supergirl story will be tied directly to the crossover, although that is theoretically possible. We have speculated in the past that the Batwoman series seems likely to be set on Supergirl's Earth.

Other popular Elseworlds stories inlude Justice League: The Nail, in which the world develops entirely without Superman after Jonathan and Martha Kent never find the baby Kryptonian; Kingdom Come, which sees the classic generation of DC heroes come out of retirement to whip their ultra-violent replacements into shape; and Gotham By Gaslight, a Victorian mystery featuring Batman which was recently adapted as a feature-length animated movie.

If the "Elseworlds" story really is an alternate-reality tale, it would make sense to exclude DC's Legends of Tomorrow, which shares a universe with the other shows but will not be participating in this year's crossover, because alterations to the timeline are kind of their whole raison d'etre, which would make the whole story feel like just an extended Legends episode of the team were in attendance.

The "Elseworlds" Arrowverse crossover will take place across three nights, kicking off on Sunday, Dec. 9th on The Flash at 8 p.m. ET. It continues on Arrow Monday, Dec. 10th at 8 p.m. and then finishes up on Supergirl Tuesday, Dec. 11th at 8 p.m. ET.