Chyler Leigh and David Harewood have joined the growing cast of CBS' Supergirl as two popular characters from the DC Comics, Alex Danvers and Hank Henshaw, a.k.a. Cyborg Superman. TV Line reports that Chyler Leigh's Alex Danvers is the foster sister to Kara Zor-El (Melissa Benoist), "whose fascination with her sibling's powers inspired her to become a doctor." Hank Henshaw is described as, "a onetime CIA agent who now runs the Department of Extra-Normal Operations (DEO), which tracks extraterrestrial threats on the planet Earth."

The actors join Melissa Benoist as the title character, Mehcad Brooks as Jimmy Olsen, Kara's neighbor and co-worker at CatCo, Calista Flockhart portraying CatCo founder Cat Grant and Laura Benanti as Kara's Kryptonian mother, Alura Zor-El. We also reported earlier this week that the show is seeking a "photo double" for an actor to play Kara's Kryptonian cousin Superman, although it isn't known how large or small the role may be. It also isn't known if David Harewood's Hank Henshaw will eventually become Cyborg Superman on the show or not.

The series is also bringing on Andrew Kreisberg alongside Greg Berlanti, Ali Adler and Sarah Schechter. The news isn't terribly surprising, since both Greg Berlanti and Andrew Kreisberg co-created and executive produce The CW hit shows Arrow and The Flash. There have been rumors that Supergirl may cross over with Arrow and The Flash, but they were shot down by CBS.

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Chyler Leigh most recently starred in the NBC summer series Taxi Brooklyn, which failed to earn a second-season renewal. David Harewood is best known for starring in Showtime's Homeland and ABC's Selfie. It isn't known when production will begin on Supergirl at this time.