ByLiam Dixon, writer at Creators.co
Awkward geeky teen writer. Form an orderly queue ladies
Liam Dixon

With Supergirl now airing on the CW, many have wondered how she will factor into the CW's Greg Berlanti universe. The news of the shows network jump was followed by the announcement of a four-part crossover that will include Arrow, Flash, Legends of Tomorrow and Supergirl. Marc Guggenheim has now confirmed that Supergirl will be at the center of this crossover event and that her actions will cause many events to unfold throughout the crossover.

Speaking at Comic-Con, Marc Guggenheim, writer, and co-creator of Arrow and Legends, revealed just how Supergirl will fit in with the other CW shows:

"It’s an external threat from outside the shows that will involve Supergirl coming over to 'The Flash', then 'Arrow' then 'Legends of Tomorrow'."

It's already been confirmed by both show's creators that Supergirl will still be in a separate universe (Barry Allen explains the multi-verse above) when all four shows return in October. So how does Supergirl end up within the Berlanti-verse? And what outside threat is causing her to crossover to each of the three shows? Here are a couple of theories...

Flashpoint Will Affect Supergirl

With The Flash being the first show that Supergirl will crossover to, it is a safe bet that Flashpoint will greatly affect Supergirl's universe. A fan favorite theory is that Barry will screw with the timeline so much that he causes his earth to vibrate at the same frequency as Kara's — an idea that was hinted at during the Supergirl/Flash crossover — which in turn causes the two earths to coexist.

This would theoretically cause Supergirl to coexist with the rest of the CW shows, but what ramifications would it have? Will the rest of Earth One think that Supergirl has existed within their would this entire time and vice versa? Will the heroes be the only people to remember both realities, just as Barry was the only person to remember both timelines after Flashpoint? It would certainly make for great storytelling and will be interesting to see how it affects each show. Legends of Tomorrow, especially could get interesting, as the timeline of that show is already in constant flux.

The universes colliding will certainly cause the outside threat from Supergirl to crossover to all shows. While we know it will be a threat that is exclusive to Supergirl and won't be connected to the other shows (sorry guys, no Flashpoint war) so what sort of threat will cause the heroes from all shows to join forces?

The White Martians Are Coming

Remember when that White Martian attacked a rally in Supergirl last season and vowed that many more of its kind will come to destroy Earth? He wasn't bluffing. The White Martians will definitely play into Supergirl season two in a big way, and don't be surprised to see them become the "external threat" that Guggenheim teased.

With the Justice Society of America confirmed to be the main focus of Legends, expect the Society to be formed from the aftermath of the Martian invasion. In the Justice League animated series, the league was formed after a Martian invasion almost devastated Earth. With this crossover bringing Supergirl, Flash, and Green Arrow together, it is safe to assume that the three of them become the trinity that creates the Justice Society of America.

With Supergirl now coexisting within the same universe as Flash and Green Arrow, we can now have a society that could include Martian Manhunter, Red Tornado, and even Superman, if Geoff Johns allows Tyler Hoechlin to appear more frequently as the Man of Steel.

We now have a very diverse roster of heroes in the ever-expanding DC Television Universe. A universe that is set to get even bigger with the inclusion of the Legion of Super Heroes teased on Supergirl, and the Justice Society of America being mainstays on Legends of Tomorrow. Who knows, maybe we will get a Hall of Justice based in Star City now that Oliver is Mayor? There is no doubt that Supergirl's inclusion into this universe will have some major implications for the future of the DCTV Universe, and the future is certainly looking bright.

What do you think Supergirl's transition may mean for all our favorite CW superhero shows?