[Spoilers for Supergirl 'Medusa' ahead]
Ever since it was announced Supergirl would be making the jump from CBS to The CW, the home of the show's fellow DC TV offerings in the Greg Berlanti universe, fans wondered how the network would unite Kara Danvers (Melissa Benoist) with her fellow superheroes. Of course, last season's crossover with The Flash established a partnership between the Girl of Steel and Barry Allen (Grant Gustin) -- as well as his ability to traverse between alternate Earths. Now, this week Kara will head to Earth-1 with Barry to help him and his friends take on an alien foe.
With the crossover having kicked off in tonight's episode of Supergirl, 'Medusa', the episodes of The Flash, Arrow, and Legends of Tomorrow will see the DC TV superheroes face off with a race of aliens known as the Dominators, in a storyline adapted from the 1980s miniseries event 'Invasion!'. However, though it seems the Dominators will only be attacking Earth-1 in the Arrowverse crossover, the alien antagonists will return to Supergirl later this season.
During a Q&A with press attended by CBR, Supergirl executive producer Andrew Kreisberg -- who additionally serves as EP on Arrow, The Flash, and Legends of Tomorrow -- teased a return of the Dominators. He said, “This is not the last you’ve seen of The Dominators. The Dominators will return on Supergirl later this season.” With Supergirl heading into the show's midseason break, though, the alien race's appearance presumably won't happen for some time.
Of course, as revealed in the latest episode of Supergirl, 'Medusa' sets up the Arrowverse crossover through a brief scene in which Barry and Cisco Ramon (Carlos Valdes) arrive in Kara's apartment and recruit her for their cause; ostensibly, the favor is repayment for Barry helping Kara last season. But, the Dominators don't make an appearance in the episode since they are the problem of Earth-1 and, so far as The CW DC TV viewers know, are not capable of traveling to alternate Earths.
As such, it's unclear whether Kreisberg's tease for the Dominators' return means Supergirl viewers will meet an alternate version of the aliens on Kara's Earth. Since the Dominators form the Alien Alliance with Daxamites and other races in 'Invasion!', perhaps Supergirl will reveal Mon-El's (Chris Wood) people have not been completely wiped out. Or, the Dominators that will appear on Supergirl may be the same race of aliens that Kara and her superhero friends face in the Arrowverse crossover. Perhaps, the Dominators may be seeking vengeance on Kara for her role in (presumably) thwarting their invasion of Earth-1.
That said, aside from Kreisberg's confirmation that the Dominators will appear on Supergirl later this season, little is known about their return; it remains to be seen how and why the alien race head to National City. But, with three more nights of The CW's massive DC TV crossover yet to unfold, there's still plenty more 'Invasion!' to come before the Dominators return to terrorize the Girl of Steel.
Supergirl returns from its midseason break with the Kevin Smith-directed ‘Supergirl Lives’; 'Invasion!' continues Tuesday November 29 with The Flash at 8pm on The CW, Arrow on Wednesday, and Legends of Tomorrow on Thursday.