Chyler Leigh is best known for playing Doctor Lexie Grey on ABC's long-running television series Grey's Anatomy. Her character was killed off several seasons ago and now she has a new gig on Supergirl. She'll be playing Alexandra "Alex" Danvers, Supergirl/Kara's (Melissa Benoist) foster sister. She is described as being "fascinated by Kara's powers from a young age" which led her to developing "a lifelong obsession with science."
Homeland and Selfie actor David Harewood has been cast as CIA agent Hank Henshaw. Henshaw is in charge of the Department of Extra-Normal Operations (DEO), "which tracks extraterrestrial threats on the planet Earth." The name Hank Henshaw should perk up the ears of comic book fans as the name is the same as the person that would eventually become Cyborg Superman.