Odette Annable as Samatha Arias/Reign (season 3, special guest season 5).

Katie Mcgrath as Lena Luthor (seasons 3-6, recurring season 2).

Floriana Lima as Maggie Sawyer (season 2, special guest season 3).

Chris Wood as Mon-El/Valor (seasons 2-3, guest season 1, special guest season 5).

Calista Flockhart as Cat Grant (season 1, special appearance seasons 2-6).

David Harewood as J'onn J'onnz/Martian Manhunter (seasons 1-6).

Jeremy Jordan as Winn Schott/Toyman (seasons 1-3, special guest season 5).

Chyler Leigh as Alex Danvers (seasons 1-6).

Mechad Brooks as James Olsen/Guardian (seasons 1-5).

Melissa Benoist as Kara Danvers/Supergirl (seasons 1-6).

James becomes the masked streetfighting vigilante Guardian Alex begins dating Maggie Sawyer and J'onn befriends a younger Martian, M'gann, from the White Martian race that killed his people. At the same time, Kara becomes friendly with Lillian's stepdaughter Lena Luthor, the new CEO of LuthorCorp, and struggles with romantic feelings for recent Earth arrival Mon-El, a survivor and prince from Krypton's neighboring planet Daxam.

In the second season, Kara and her allies deal with feuds between Earth's native populace and extraterrestrial community, and investigate the shadowy organization Project Cadmus, masterminded by Lillian Luthor, mother of Superman's archenemy Lex Luthor. She is aided by a few close friends and family who guard her secrets, including her cousin's friend, James Olsen, and tech genius Winn Schott, Jr. She and her adoptive sister, Alex Danvers, discover that their boss, Hank Henshaw, is actually benevolent Green Martian J'onn J'onzz. Kara discovers that hundreds of the criminals her mother prosecuted as a judge are hiding on Earth, including her aunt Astra and Astra's husband Non. In the first season, having hidden her powers for more than a decade, Kara is forced to reveal her powers, and becomes National City's protector. The series begins eleven years later when the now 24-year-old Kara is learning to embrace her powers and has adopted the superheroic alias 'Supergirl'.

By the time the spacecraft crash landed on Earth, Kal-El had grown up and become Superman. Kara was meant to protect her infant cousin Kal-El, but her spacecraft was knocked off course and forced into the Phantom Zone, where it stayed for 24 years. Kara Zor-El was sent to Earth from Krypton as a 13-year-old by her parents Zor-El and Alura.

Arrow season 5 wikipedia