Spoilers ahead for the Season 3 finale of Supergirl.
The third season of Supergirl only just came to an end, but the finale changed the game in some big enough ways that it's already worth looking ahead to Season 4. The finale ended with Winn and most of the Legion of Super-Heroes off to the future, Brainiac 5 as Winn 2.0 at the D.E.O., James outed as Guardian, J'onn retiring from the D.E.O., Alex taking over his old job, Alura returning to Argo City, and a Kara doppelganger landing in Siberia to kick off Supergirl's version of the Red Son story from DC Comics lore. Now, while the loss of Winn as a regular means that he won't be around as much in Season 4, he will be back. The future isn't quite so certain for other characters. So, read on for our picks of 7 Supergirl characters that need to come back next season!
President Olivia Marsdin
Olivia Marsdin made her Supergirl debut back in the beginning of Season 2 as the President of the United States. She arrived in National City to sign a decree that would grant the rights of U.S. citizens to aliens, which understandably endeared her to Kara. The end of her first episode revealed that President Marsdin is actually an alien herself. She popped up a couple of more times in Season 2 but was absent from Season 3. Episodes with Olivia Marsdin in the mix are always fun. Throw in the fact that she's played by none other than TV Wonder Woman Lynda Carter, and she needs to come back.
Supergirl is obviously the story of the Girl of Steel rather than her more famous cousin, but the show has proven that it can handle including the Man of Steel in episodes without overshadowing Kara. Tyler Hoechlin can tackle both the charming clutziness of Clark Kent and the dashing superhero Superman. He's a fun Superman that can't necessarily be found in other superhero projects, and the team-ups between Clark and Kara are always entertaining. Now that Supergirl proved Superman can appear without taking all the spotlight, Supergirl should totally bring him back. Although we don't need 23 episodes of Superman per season, there's room for him to drop in from time to time.
Season 3 dropped a big Zor-El family bombshell with the reveal that Kara's parents hadn't actually both died when Krypton was destroyed. Due to a lot of luck and Kara's father's willingness to sacrifice his life to save others, Alura and many other Kryptonians survived in a contained Argo City that survived the planet's destruction. Alura joined Kara on Earth for the big climactic fight against Reign and Co. in the Season 3 finale, but she returned to her people on Argo City at the end. It simply wouldn't make sense if neither mother nor daughter went to the effort to reunite after spending so many years believing they'd never meet again, so Supergirl needs to bring her back. Besides, she's played by a former Lois Lane!
Cat Grant was a major part of Supergirl in its first season, but she was no longer a series regular after Supergirl made the move to The CW and production moved to Vancouver from California. Actress Calista Flockhart chose not to uproot her life to continue working on the series, and her appearances on the series since have been few and far between. She was last seen on TV in-universe as President Marsdin's press secretary, so surely it would make sense for her to pop back into the story in Season 4. Maybe Calista Flockhart and Lynda Carter can reprise their roles in the same episode! President and press secretary could travel to National City together.
Jeremiah Danvers has popped in and out of Supergirl throughout its years on the air, and his loyalties are never 100% certain. Whether he's missing, presumed dead, on the run, blackmailed, or brainwashed, he always mixes things up. Unfortunately, Alex and Kara tend to have rough rides whenever Jeremiah turns up, but plots certainly thicken when he's around. Besides, there's something very enjoyable about having the Clark Kent from Lois & Clark playing Supergirl's foster dad. Unfortunately, the death of Daxamite Queen Rhea means that Supergirl probably won't be able to deliver the Lois & Clark reunion between Cain and Teri Hatcher. Still, Cain could be a worthy addition nonetheless if he comes back.
Unlike the other folks on this list, Lex Luthor has technically only appeared via flashback as of the end of Season 3. A teenage version of Lex appeared in a blast from the past when Lionel Luthor brought a young Lena home to Lex and Lillian. Lex and Lena played chess together, and they seemed to get along well enough from what little we saw. Given that Lex would go on to become a supervillain convicted of 32 life sentences, obviously something went very wrong along the way. Lex should definitely return, either in flashback or as an adult. More on Lex could develop Lena further, and Katie McGrath has a pitch for who should play him. If Supergirl can include Superman without overshadowing Kara, surely the show can include Lex without overshadowing Lena!
Alura may not be able to leave Argo City every weekend and Jeremiah Danvers may remain in the wind, but they're not the only parental figures who could drop back into Kara's (and Alex's) life! Eliza Danvers could always play a role in the series, whether because she's in the thick of the action in National City or simply because her girls need a break from their lives and come home to Midvale to nurse their broken hearts. Helen Slater is always wonderful in her scenes with Melissa Benoist and Chyler Leigh, and Eliza has skills as both a mom and a bio-engineer. Eliza also has the means to turn up without traveling through time and/or space, so Supergirl should absolutely bring her back.
Honorable Mention: Mon-El
Winn wasn't the only main character to take off with the Legion of Super-Heroes at the end of the Season 3 finale. Mon-El also took his leave of 2018, and unlike Jeremy Jordan, Chris Wood isn't staying on board as a recurring star. Supergirl executive producer Robert Rovner has said that the show would love to have him back at some point. Still, Mon-El only gets an honorable mention because Kara may be better off if he's not around for at least Season 4. She had a hard time getting over him and moving past him in Season 3; she might have an easier time if Mon-El is off saving the day in another time and another place.