Supergirl premieres for the first time on The CW next week, after her debut season aired on CBS. The more youth-oriented network seemed a natural destination for the Kryptonian, as she'll join the DC superheroes already present in the primetime line-up. Supergirl even gets the honor of kicking off the schedule each week on Monday, followed by The Flash, Arrow, and Legends of Tomorrow on successive nights.
Despite their comic book connections, Supergirl exists on a very different Earth than the other three CW shows. Kara (Melissa Benoist) did not even know of the existence of The Flash (Grant Gustin) until he catapulted into her world from an alternate universe. That crossover episode earned praise and a significant boost in ratings, so fans naturally wondered if the move to the same network meant that -- possibly by virtue of that Flashpoint storyline -- Kara would also move fully into the Arrowverse.
Executive producer Andrew Kreisberg has finally provided the answer for us, and as many may have suspected, that four-series crossover event is going to be the prime example of how these shows will mesh. As the showrunner explains in an interview with Entertainment Weekly, any shift in time and space will be "not for her entire world, but Kara will be traveling from her dimension to our dimension, 'our' being the world that The Flash, Arrow, and Legends lives in."
As Supergirl shifts from filming largely in studios in L.A. to a wider array of location shoots in Vancouver, the show will widen its scope to include more alien encounters. Kreisberg says season 2 won't be all about Fort Rozz aliens, but "a whole universe of species, creatures, invaders and explorers that make pit stops on Earth, a little like Men in Black." It makes sense, then, that Supergirl will take part in an Arrowverse crossover that features an alien race known as the Dominators.
While bringing Supergirl completely into the shared universe with the other heroes would mean more opportunities for fun crossovers, it makes sense that the show wouldn't do a full overhaul after one season. All the shows playing in the exact same sandbox starts to limit the stories that are available, and also makes it difficult for the writers to keep all the timelines in sync on four series; something they've already struggled with in the past on more than one occasion. So viewers will literally have the best of both worlds, with Kara battling a whole horde of aliens in her own universe, and on occasion flying in to the Arrowverse to take on new, and hopefully entertaining, challenges.
The Flash season 3 airs Tuesdays at 8pm on The CW, Arrow season 5 airs Wednesdays in the same timeslot, Supergirl season 2 debuts Monday October 10, and Legends of Tomorrow season 2 on Thursday October 13.