The CW's Supergirl season 5 casts Mitch Pileggi (The X-Files) and Cara Buono (Stranger Things) as characters most often associated in DC Comics with the underwater civilization of Atlantis. At the end of season 4, Lena Luthor (Katie McGrath) finally discovered that Kara Danvers (Melissa Benoist) is, in fact, Supergirl. The season finale suggested that this discovery will put Lena at odds with Kara in season 5.
But Supergirl will have much more than Lena to deal with in the new season. She will also be part of the most significant crossover event to ever air on The CW. That event, Crisis on Infinite Earths, will include all five shows within the Arrowverse, including the upcoming Batwoman. Supergirl will also get a new costume for season 5, as well as a few new cast members: Julie Gonzalo and Staz Nair.
That's not all, though. Deadline reports that Supergirl will get an additional two recurring cast members for its upcoming season. Although both characters' descriptions are as members of an "ancient alien" race, in DC Comics, they are actually from Atlantis. Pileggi will portray Rama Khan, one of the ancient rulers of Atlantis. He has the power to control all four elements (fire, water, earth and air) to protect the Earth from humankind. Buono will portray Gamemnae, who co-ruled Atlantis with Rama Khan in the comics. She uses technology to control humans. Both characters' motivations will have them going up against Supergirl.
Rama Khan and Gamemnae first appeared in 2002 in DC Comics' JLA as ancient Atlanteans. However, the Supergirl TV show seems more focused on calling them "ancient aliens." Perhaps their origin stories are different from the comics, although The CW may be hiding their Atlantean roots for a later surprise reveal to fans. The Supergirl TV series is no stranger to Atlantis. A 2017 tie-in novel called Supergirl: Age of Atlantis explored a story following an intelligent sea creature captured by the Department of Extranormal Operations (DEO). That book also confirmed the existence of Aquaman in that universe.
Being that the Aquaman movie was such a hit for DC, it makes sense to capitalize on that interest through one of The CW TV shows. A potential storyline would probably not connect to the Aquaman film in any way, but a different version of Atlantis could easily exist on the Supergirl series. It would be a way to keep fans interested in the show, even if the Atlanteans in question become enemies of Supergirl.