Supergirl is a superhero action-adventure drama series developed by Ali Adler, Greg Berlanti & Andrew Kreisberg, starring Melissa Benoist in the lead role.
The show's first season aired on CBS from October 26, 2015 until April 18, 2016. In May of 2016, it was announced that the show would be moved to the CW Network and the second season is scheduled to air on October 10, 2016.
Kara Zor-El (Melissa Benoist) was sent to Earth from the doomed planet Krypton as a 12-year-old by her parents Zor-El (Robert Gant) and Alura (Laura Benanti). Alura gave her instructions to protect her infant cousin Kal-El, and informed her that like her cousin, she would have extraordinary powers under Earth's yellow sun.
While en route to Earth, Kara's spacecraft was diverted by a shock wave from Krypton's explosion and forced into the Phantom Zone, where it stayed for 24 years. During this period, time stopped for Kara so, when the spacecraft eventually escaped the Phantom Zone, she still appeared to be a 13-year-old girl.
By the time the spacecraft crash landed on Earth, Kal-El had grown up and become Superman. After helping her out of the craft, Superman took Kara to be adopted by his friends, the Danvers family. The main series begins more than a decade later when the now 24-year-old Kara is learning to embrace her powers after previously hiding them.
Kara hid her powers for more than a decade, believing that Earth didn't need another hero, but she has to reveal her powers to thwart an unexpected disaster, setting her on her own journey of heroism as National City's protector.
Kara discovers that hundreds of the criminals her mother prosecuted as a judge on Krypton are hiding on Earth, including her mother's twin sister Astra (also played by Benanti) and Astra's husband Non (Chris Vance), who seek to rule the world.
After briefly becoming suspicious of the true agenda of her boss, Hank Henshaw (David Harewood), she and her adoptive sister Alex Danvers (Chyler Leigh) secretly discover that Henshaw is actually a benevolent alien refugee, J'onn J'onzz, who has resided on Earth for over fifty years after escaping a holocaust on his homeworld of Mars.
J'onn infiltrated the DEO to reform the organization as well as to watch over both Alex and Kara in addition to guiding the latter in the use of her powers due to his experience with his own abilities.
Kara is also being targeted by Earth's criminals as the result of her being related to Superman, and later on encounters an emerging community of metahumans and individuals from parallel universes. In the process, she accumulates her own rogues gallery who seeks to defeat and destroy her and is is aided by a few close friends and family who guard her secrets—most notably her cousin's longtime friend, James Olsen (Mehcad Brookswhich also serves as a major plot in high tech mogul Maxwell Lord's (Peter Facinelli) scheme to expose Kara's identity.
- Melissa Benoist as Kara Zor-El / Kara Danvers / Supergirl: A 24-year-old Kryptonian living in National City, who must embrace her powers after previously hiding them. She assists her adoptive sister as part of the Department of Extra-Normal Operations (DEO) as she discovered the truth that her foster father also worked for the DEO so they would not take her, while Alex's co-workers at the DEO help her perfect her powers. Kara works as Cat Grant's assistant at CatCo. Benoist expressed her excitement over portraying the character, and being able to "[tell] a story about a human being really realizing their potential and their strength". Malina Weissman portrays a young Kara.
- Mehcad Brooks as James Olsen: A former Daily Planet photographer, James moved to National City and became the new art director for his former colleague, Cat Grant, at CatCo Worldwide Media. He is a potential love interest for Kara. Among his reasons for moving across the country include his breakup with his fiancée, Lucy Lane, and keeping an eye on the newly revealed Supergirl for Superman. While working at the Daily Planet, James received the Pulitzer Prize for taking the first photograph of Superman.
- Chyler Leigh as Alex Danvers: Kara's adoptive sister. She is a doctor and scientist who works for Hank Henshaw at the DEO. Having been extensively trained in combat after joining the DEO, Alex in turn provided rigorous training to Kara in order to decrease her reliance on her powers. Initially, like Kara, she becomes suspicious of the DEO and thus her own role upon learning of their father having worked there in order to protect Kara, but Alex ultimately learns that Henshaw is the Martian survivor J'onn J'onzz in shape-shifted disguise, whom her late father had rescued before his and the real Henshaw's deaths. Jordan Mazarati plays a young Alex.
- Jeremy Jordan as Winslow "Winn" Schott, Jr.: A tech expert who works alongside Kara at CatCo, he serves as one of her allies, helping her develop her costume and aiding her in her adventures. Winn has an unrequited crush on Kara and is a rival with James for her affection. However, at the end of "For the Girl Who Has Everything", Winn has seemingly accepted the fact that it's best that they remain as best friends, and in "Solitude", he begins seeing Cat Grant's new assistant, who is also Kara's rival: Siobhan Smythe, who is subsequently fired by Cat and who, in "Worlds Finest", becomes a supernatural metahuman supervillain called Silver Banshee. In the series, he is the son of Toyman. Cat nicknames him Toyman Junior after she finds out.
- David Harewood as Hank Henshaw and J'onn J'onzz / Martian Manhunter: A former CIA agent and current head of the DEO, who goes on high alert when Supergirl reveals herself, worried that her otherworldly abilities pose a threat to humankind. However, the "real" Henshaw died with Jeremiah Danvers in Peru while hunting the alien J'onn J'onzz. After Henshaw died, the 317-year-old J'onzz, who has shape-shifting abilities, took Henshaw's likeness in order to reform the DEO from within as well as to watch over Alex and Kara. The evolution of Henshaw was discussed during the filming of the pilot, with the executive producers jokingly saying that Harewood would be a good actor to play the Martian Manhunter in a potential television series, to which DC Comics' Geoff Johns asked why it could not be done in Supergirl. Harewood reflected that he had difficulty "find[ing] an angle to play Hank Henshaw" in the pilot, and became excited when he was told about the change to his character's backstory.
- Calista Flockhart as Cat Grant: The shallow and superficial founder of the media conglomerate CatCo Worldwide Media, who feels, since she "branded" Kara as "Supergirl", that she has proprietary custody over the new hero. Before she founded CatCo, she was a gossip columnist at the Daily Planet, and before that, the personal assistant to the Daily Planet's Editor-in-Chief, Perry White. Cat investigates and reveals that Supergirl is Superman's cousin, which then causes Kara to become a target for some of Superman's rogues gallery. Cat also serves as a mentor to Kara, dispensing advice about being a woman in a man's world. In the episode "Hostile Takeover", she suspects that Kara is Supergirl.
- Floriana Lima as Maggie Sawyer: A detective for the National City Police Department who takes a special interest in the cases involving aliens and metahumans.
- Chris Wood as Mon-El: A superhero with similar powers to Superman and Supergirl from the planet Daxam, Mon-El lands on Earth in the pod at the end of season one.