In the mid-season finale, Supergirl was badly beaten by Reign, a new villain that is secretly her friend, Samantha. Reign's purpose is to be a sleeper agent of the Kryptonian Worldkillers. The beatdown was very public, and witnessed by her friends at the DEO, including her ex-boyfriend, Mon-El who has been living in the future as a member of the Legion Super-Heroes, with his wife, Saturn Girl. Four more Legionnaires remain in stasis pods on their trapped ship. In this episode, Mon-El awakens another Legionnaire to help Supergirl while Reign continues to wage destruction on National City. Oh, spoilers abound.
In the current season of Supergirl, the Legion of Super-Heroes is slowly revealing itself to be a big part of the story with Supergirl fighting the Kryptonian threat of Reign. Mon-El, introduced last season as an eventual love interest for Supergirl, vanished at the end of last season due to lead poisoning from Earth's atmosphere. Now, announcements have been made for casting two members of the Legion, Saturn Girl, already appearing in two episodes, and Brainiac 5, traditionally a love interest for Supergirl from almost his first appearance. Spoilers abound after here, so don't say you were weren't warned.
This season of The Flash looks to be one with plenty of Easter eggs for comic book fans. Already two episodes in and we have had Atom Smasher, Jay Garrick and references to numerous other comic book characters. This week's episode "Flash of Two Worlds" was ripe with references to various comic book stories.