The more details we get about The CW's forthcoming December crossover event, the more likely it seems that the crossover -- and the network's subsequent Batwoman TV series -- will take place on Earth-38, the home of Supergirl.
Since the first time Supergirl came to Earth-1 during the "Invasion!" crossover, fans have wondered when The Flash and Green Arrow might make their way to her Earth, so they could spend some time hanging around with Superman, The Guardian, and the rest.
Now, it seems likely that is what will happen...and it has both practical and storytelling implications for this season and beyond -- not the least of which is that it seems likely Batwoman will appear on Earth-38, and that her planned spinoff will therefore share real estate with Supergirl more than the other series.
No announcement has been made as yet with regard to what Earth Ruby Rose's Kate Kane will populate, but the evidence seems to be leaning in the direction of Earth-38, and here's why:
Earlier today, The CW announced that Lois was being cast to appear opposite Tyler Hoechlin's Clark Kent/Superman in the December crossover.
Lois, intrepid reporter that she is, could theoretically hitch a ride with Superman over to Earth-1...but it seems unlikely.
The more likely scenario is that Earth-38 will play host to the crossover, with Lois likely breaking the remarkable story that a multiverse exists.
For starters, there is no DC's Legends of Tomorrow (we'll get to that soon). For another thing, the time slots are all moved around to accommodate a three-day event that begins with The Flash and ends with Supergirl.
The fact that the three-part story ends with Supergirl may be telling: last year, the writers worked together to craft a crossover that felt more like a three-part movie -- which worked well because the finale centered on the death of Martin Stein, a cast members since the pilot DC's Legends of Tomorrow, and that story took place on Legends, giving it room to breathe.
It would not be difficult to imagine this year's crossover being similar, with Supergirl subbing in for Legends as the series that will have the most long-term impact following the introduction of Gotham and Batwoman to the mythology.
Recently, The CW announced that the Legends would not take part in the annual crossover event. The official explanation for this is that Legends of Tomorrow has become so tonally different from the other shows that it can be jarring to put those characters among the more serious Arrow and The Flash characters.
Practically speaking, it means one less cast to try and work around in the crossover, and work into the story, which likely means a little less time and stress spent making the crossover, which last year left the cast and crew of every show dazed and exhausted.
The Legends also exist outside of the timestream and often make their way into stories only when they know things are dire and they can be of use. It could be that, if the story is taking place on Earth-38, the Legends either have no way of knowing what threat is facing down that alternate history, or at least aren't looking at it.
Gotham City not only is a place on Earth-38, but has been name-checked several times.
Compare that to Earth-1, where Cisco creates a "Flash Signal" inspired by Commissioner Gordon's vigilante-summoning spotlight and says he got the idea from a comic book.
Yes, it seems that there is a Gotham City on Earth-1 as well. While it has not been as explicitly referenced as it has on Supergirl, the Waverider's time-traveling destination plate has been known to flip past Gotham, and one of the Clocks in the Central City Picture News newsroom was timed to Gotham's time zone.
It would not be surprising for The CW to tease some kind of potential romance between Alex Danvers and Kate Kane, especially since one of Kate's major canonical love interests, Renee Montoya, is so tied into the Batman mythology that she may not be available. The other, Maggie Sawyer, has already appeared and disappeared on Supergirl.
But even if they did not do that, teaming Batwoman and Supergirl could be a regular event, something that could bring together some big numbers for the network without the logistical headaches of the more massive crossovers.
It could also, at least in theory, preclude Batwoman and Supergirl from having to take part in all of the crossovers and give the opportunity, at least once in a while, to leave everyone on their own Earths and still enjoy ratings pickups from smaller team-up events.