Supergirl is one of the best comic book-based shows on TV -- and while it's not always the most comic book-accurate (we're looking at you, Cyborg Superman and Mister Mxyzptlk), it mixes the fun and uplifting spirit of the Silver Age with the high-stakes and emotional core of modern superhero storytelling. Though not much is known about the show’s upcoming third season aside from the fact that Reign will play a part as the main villain, there’s a good chance Supergirl may live up to a promise stretching back to its first season, and send Kara Danvers all the way to the thirty-first century to hang out with the Legion of Super-Heroes.
Supergirl has been teasing the Legion's arrival since the first season when Kara visited the Fortress of Solitude and among its many artifacts was a Legion flight ring. Since then, there have been hints both on and off the show, with Supergirl herself, Melissa Benoist, noting, “The Legion Ring, I believe, is on its way -- but I don’t know exactly when," when asked about the team by TV Line.
The finale of Supergirl's second season may have provided a path to the 31st century for Kara, as Mon-El was pulled into a mysterious portal on his way out of Earth’s orbit. It’s more than likely that portal either leads to the Phantom Zone or directly to the 31st century itself, but either way, it wouldn’t be too surprising to see Kara journey to the future and find her lost love waiting for her when she gets there.
Adding the Legion to Supergirl even for a couple of episodes opens up the opportunity for dozens of new character interactions and provides Kara the opportunity for new superhero friends to relate to that she doesn’t have back home. Martian Manhunter and Superman are both more parental figures than friends, and aside from them, everyone she meets with powers is usually trying to kill her. It would be a positive experience for her to hang out with Saturn Girl, Bouncing Boy and Triplicate Girl and relate to heroes who know what she goes through.
Supergirl could also add its own speedster to the ranks and somewhat tie into the Flash’s legacy by bringing in XS, who in the comics is Barry Allen’s granddaughter and cousin to Bart Allen, AKA Impulse. While we’re likely to never see the Earth-Supergirl incarnation of Barry Allen, it would be nice to hint that he’s out there somewhere and he still has a legacy within the Speed Force, even if he doesn’t become The Flash in this particular timeline.
The addition of the Legion of Super-Heroes also brings opportunties to spice up the one place Supergirl has always felt incredibly lacking: Kara’s love life. Her season one relationship with James always felt forced and her uncontrollable love for Mon-El was unconvincing for most of season two. However, while bringing Kara to the 31st century would reunite her with Mon-El, it would also bring in one of Kara’s most enduring romantic interests from the comics, Brainiac 5.
While most of Kara’s romantic pursuits have been uninteresting and hardly captivating, introducing a futuristic love triangle in season three would present new opportunities and new dilemmas for Supergirl, both romantically and ethically. She’s already faced off with Brainiac 8 and knows of the original’s reputation, so what kind of thought process would she go through when confronted with a “good” Brainiac that she shares an undeniable connection with?
The time-jump to the 31st century also opens up the list of villains Supergirl could face, mixing things up from the usual “secret alien in National City” formula the series has found itself in. The current Supergirl comic has pitted Kara against The Emerald Empress in the present day, but it takes an entire Legion of Super-Heroes to take on the Fatal Five in the future, and who knows, maybe one or two villains make the jump back to the present day to cause some trouble for Kara in her home timeline.
One of the best things about the Legion is its massive roster, and a show like Supergirl would be able to exploit that incredibly well. Imagine an episode all about Supergirl having to team-up with the Legion of Substitute Heroes, or a Supergirl/Matter Eater Lad team-up. We already know that Superman has met the Legion because their flight ring is in his Fortress, but what if some wires get crossed and Kara ends up hanging out with a teenaged Superboy who has just met the team? It would switch-up the dynamics in a fun way and give Kara a chance to impart some important lessons to the cousin she never got the chance to watch grow up.
If the Legion of Super-Heroes did show up, it would certainly be exciting, but why should Supergirl get all the fun? After last years “Invasion!” crossover between Supergirl, The Flash, Arrow and Legends of Tomorrow, this year’s inevitable event has to go even bigger. So what’s bigger than a jump one thousand years into the future? Imagine seeing Barry Allen interact with perpetual do-gooder Cosmic Boy, Green Arrow compare stubble with Lightning Lad and White Canary go toe-to-toe with Karate Kid. There are so many opportunities to make the extended Arrowverse even bigger and better with the Legion, and Supergirl is the link to get it there.
There’s always the dream that the Legion turns out to be so popular that it gets spun off into its own show, too; it’s such a large cast that it would be shame to waste it on what would be a handful of episodes in Supergirl's third season. A backdoor pilot situation would allow The CW to gauge the interest in the Legion as a franchise, and also compare it to CBS All-Access' upcoming Star Trek: Discovery, to see if the appetite for far future sci-fi is there among audiences. The CW shows excel at team dynamics and soap opera storytelling with high-stakes superhero settings, which describes the Legion of Super-Heroes to a tee. No other DC Comics property fits The CW’s mold more than the Legion, and if the network introduces the team in Supergirl’s third season, it might have the next breakout hit on its hands.