The first season of Supergirl teased the the Legion of Super-Heroes when it showed us a golden Legion ring in Superman's Fortress of Solitude. The second season then introduced a new character to the show's cast, Mon-El, a Daxamite alien who has quite a long history with the time-traveling team of heroes in the comics. Now, season 3 of Supergirl is just about to resume, with a story that will fully introduce the Legion to the series' mythology. We've already caught glimpses of Brainiac 5, Saturn Girl and Mon-El in full Legion costume, with many more to come.

In the comic books, the Legion of Super-Heroes first appeared in 1958, in Adventure Comics #247. Created by Otto Binder and Al Plastino, the team of teenagers was only slated for that one appearance. However, the characters proved popular enough that they would eventually get their own title, effectively helping them become an important thread in the DC Universe tapestry. The Legion have had a very long history in the comic books, and some aspects of their long career may have been forgotten along the way. Here, CBR revisits the history of the Legion -- past, present and future -- to list 15 forgotten facts that you should know about the team.

15 THE LEGION RINGS ENABLE FLIGHT (AND OTHER POWERS)

Legion Flight Rings on Supergirl

To be a member of the Legion of Super-Heroes, one needs to have superpowers, obviously. These powers vary greatly from one member to the next, and yet there is one ability that all members share: flight. While some might have the natural ability to fly, most of the Legionnaires don't. Their Legion rings are actually what allows them to defy gravity.

In fact, one need not even be a Legionnaire to use the ring – one just needs to get ahold of one. This is actually how the superhero known as Booster Gold is able to fly. However, granting the ability to fly isn't all that these rings can do. They can also work as flashlights and communication devices, and can be used to lift people and objects, protect from telepathic attacks and send out distress calls.

14 THEY STARTED OUT AS A CLUBHOUSE

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The Legion members hail from the 30th and 31st century. In their first appearance, they time-traveled to the present to recruit Superboy to their ranks. When they were first introduced, the Legion members, Cosmic Boy, Lightning Boy and Saturn Girl referred to themselves as a super-hero club. In the future, the story of Superman had inspired them to become superheroes, and to help those in need with their powers.

Over time, the Legion became a more daring and gritty super-team, but at first, they were no more than teenagers with a club. Their headquarters was in an upside down spaceship, and they would have to come a long way to evolve into a truly formidable team of adults. In fact, perhaps in a bid to reflect that, one of their founding members would have their name changed to Lightning Lad.

13 SUPERMAN IS ACTUALLY A MEMBER

Superman flying with a Legion flight ring

Although the Legion of Super-Heroes were inspired by Superman, the person they traveled back in the past to recruit was a far cry from the legend they knew. Instead, they met a young Clark Kent who was only just coming into his own as Superboy. Although the Legion would eventually head back to their own time and leave Clark Kent in his respective timeline, the young Superboy was still an honorary member of the Legion.

Even as he grew up to become Superman, Clark would always serve as a member of the Legion. The ring glimpsed in the Fortress of Solitude in the first season of Supergirl is likely a link to that fact, and it will be interesting to find out if Tyler Hoechlin's Superman had adventures fighting alongside the Legion in his past – or perhaps even his future.

12 SOME LEGIONNAIRES HAVE VERY STRANGE POWERS

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The Legion has many powerful members in its ranks. From Lightning Lad's electric powers to Mon-El's Kryptonian-like abilities, there are a great number of Legionnaires who can turn the tide of battle. However, some of the lesser known members of the super-team have some very, very strange powers to go along with their equally strange, and quite self-explanatory, codenames.

For example, there is Bouncing Boy, who actually goes about bouncing from one spot to the next. Then, there is Matter-Eater Lad who, you guessed it, can eat any type of matter. And if all that weren't enough, there is also Arm-Fall-Off-Boy, who can remove his arms at his leisure, to use as weapons (though his relationship with the Legion is tenuous at best). And yet, all of these characters have their own important spot on the team (to varying degrees), and they have proven to be crucial, if unique, additions to the Legion.

11 SUPERGIRL FIRST BECAME A MEMBER IN 1961

In the comics, Supergirl has had a very long and rich history with the Legion of Super-Heroes. She first became a member in 1961's Action Comics #276. The story, written by Jerry Siegel and illustrated by Jim Mooney, was titled "Supergirl's Three Super-Girlfriends!" and it introduced Kara Zor-El to Saturn Girl, Phantom Girl and Triplicate Girl.

The three Legionnaires take Kara to the future, where they introduce her to the rest of the team and make her a full-fledged member. This began a long relationship between Superman and the Legion, one that even saw the comic book series take on the title Supergirl and the Legion of Superheroes for a while. Therefore, if anyone were to complain that the Legion has no place on the Supergirl television series, you can remind them of that little fact.

10 SATURN GIRL IS THE ONLY CURRENT LEGIONNAIRE

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In 2016, DC relaunched its entire line of comics under the Rebirth banner. After the more streamlined approach to continuity in the New 52, the DC Universe was returned to a status that was more in line with the pre-Flashpoint continuity. But although forgotten or missing elements like the original Wally West were brought back to the DCU, the Legion was still conspicuously missing.

However, we do know that they have some role to play in the events to come. Currently, there is only one member of the Legion active in the comics -- Saturn Girl -- and she is but a pale reflection of her former self. Currently, Saturn Girl is verging on insanity, and is locked up inside Arkham Asylum. Her Legion ring was taken away from her, and she is mumbling things about her friends, the future and Superman.

9 THEY WENT THROUGH THREE CONTINUITY SHIFTS

Since the Legion have been ingrained in DC continuity for such a long time, they went through massive shifts each and every time the publishing line went through a relaunch. It had come to a point that there were three different origin stories, with three different iterations of the team -- and no one could exactly be certain which version of the Legion was the real, official one.

And yet, it turns out that all three of these different versions were made canon, in the Final Crisis: Legion of 3 Worlds miniseries by Geoff Johns and George Pérez. The three versions of the team united against one of their greatest enemy, the Time Trapper, as well as the Legion of Super-Villains. With Superman able to unify all of these Legionnaires, it became an event the likes of which we had never seen before.

8 THE NEW 52 LEFT 7 LEGIONNAIRES TRAPPED IN THE PRESENT

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When DC relaunched its entire universe with the New 52, it streamlined its entire continuity to make its universe more approachable to new readers. In the comic book title Legion Lost, by Fabian Nicieza and Pete Woods, readers followed seven Legionnaires as they traveled to the present on a special mission. This series was different because it cut the members off from their support system.

The seven superheroes were stuck in the present, their flight rings ineffective. On top of all that, their mission involved stopping a villain from unleashing a deadly pathogen on the world that would affect the future. The Legionnaires were stranded in the present, and the series was canceled with them still very much stuck in a time that wasn't their own. It would only be a few years later that the Legionnaires would be allowed to join back with the rest of the Legion.

7 THEIR LAST COMIC BOOK APPEARANCE WAS 3 YEARS AGO

The Retroboot Legion in Justice League United

In case anyone is wondering where the Legion of Super-Heroes has been in the comics, it's important to remember that the full Legion team hasn't featured in any DC comic book for the past three years. Their last full-fledged appearance occurred in the New 52 continuity. In writer Jeff Lemire's Justice League United, the Legion arrived from the 31st century with dire news – that their own timeline, their very future, had been destroyed.

This story was titled "The Infinitus Saga," a story of both past and future. It saw the Legion Lost team – the team of Legionnaires lost in the present – finally return to the ranks of the team. On top of that, many classic Legion members teamed-up with the Justice League United to save the future, a team that featured most notably Supergirl, who obviously has quite the history with the team.

6 MON-EL WAS LEADER, AND MARRIED SHADOW LASS

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In the third season of Supergirl, when Mon-El returned to Earth from his time away, he arrived from the future, already a member of the Legion of Super-Heroes. But to complicate matters, Mon-El was now married to Imra Ardeen, aka Saturn Girl. While the identity of his wife is different, it's actually worth noting that Mon-El was in fact married to a Legionnaire in the comics: Shadow Lass.

The change on the television series may be in order to streamline the story without having to add more Legionnaires. Furthermore, on Supergirl, Mon-El explained that he helped form the Legion in the future, and we have come to understand that he is in part their leader. While Mon-El was not a founding member of the team in the comics, he did come to be its leader, for a time.

5 JIM SHOOTER FIRST WORKED ON THE TITLE IN HIS TEENS

The career of Jim Shooter, legendary comic book writer for both Marvel and DC, had a very notable start. When he was no more than 14 years old, Shooter started working on Adventure Comics, guiding the Legion of Super-Heroes on their new adventures after sending his own stories and drawings to DC Comics in 1965. His work in part helped elevate the status of Legion.

As a writer, artist and editor, Jim Shooter left a lasting mark on the Legion of Super-Heroes, during a time when the team was still in its infancy. While he was working on the title, Shooter created lasting new Legionnaires like the Karate Kid and Shadow Lass, and he also created the Fatal Five, the supervillain team that became tied with the Legion.

4 REJECTED APPLICANTS FORM THE LEGION OF SUBSTITUE HEROES

LoSH Quiz Polar Boy

Although the Legion of Super-Heroes has an open door to any and all applicants with superpowers, and although they already count many heroes with strange powers in their midst, there are those whose applications are refused. Some of these applicants' powers just wouldn't be an asset to the team. For example, Polar Boy was refused because he couldn't control his ice powers, and Stone Boy can turn to stone, but he can't move when he does.

For that reason, some of these rejected applicants formed a Legion of their own – the Legion of Substitute Heroes. This super-team doesn't see much light compared to the real Legion, but they have, throughout the years, proved to be valuable assets from time to time. However, we doubt that the Substitute Heroes will appear on Supergirl.

3 THEY FOUGHT (AND DEFEATED) DARKSEID IN THE FAR FUTURE

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One of the most famous Legion of Super-Heroes stories is "The Great Darkness Saga," by Paul Levitz, Keith Giffen and Larry Mahlstedt. The 1989 story takes place entirely in the Legion's 30th century future, with the young Clark Kent, aka Superboy among their ranks during his time away from Earth as a member of the Legion. The story is famous for pitting the Legion against the almighty villain, Darkseid.

In the far future, Darkseid re-emerges as the ultimate villain in the galaxy. If they have any hopes of defeating him, the Legion must call upon every able Legionnaire to help, both past and present. Yes, that includes Supergirl, and the Legion of Substitute Heroes. "The Great Darkness Saga" is a quintessential Legion story, one that any fan should read.

2 THE IDENTITY OF TIME TRAPPER HAS CHANGED MANY TIMES

Time Trapper Legion of Super-Heroes

The Time Trapper is one of the Legion of Super-Heroes' biggest villains. He is generally depicted as a robed and hooded character, his face shrouded in darkness, his true identity a mystery. The villain takes residence at the end of time itself and his powers of time-manipulation are what makes him such a dangerous adversary. The Legion have gone up against the Time Trapper many times.

Apparently, every time they have faced him, the identity of the person under the hood has changed. At first, the Time Trapper was revealed to be a Controller. Then, that was later changed to various other identities throughout the years, from a future and evil Cosmic Boy, to the cruel Superboy-Prime and even possibly an entire alternate universe taking human form. As it stands, no one is exactly sure who the Time Trapper truly is.

1 SUPERGIRL AND BRAINIAC 5 ARE ENDGAME

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When Supergirl was first taken to the 30th century to meet the Legion of Super-Heroes, Brainiac 5 -- the good-hearted descendant of the Superman villain Brainiac, and leading member of the Legion -- declared his love for Kara Zor-El. Although Supergirl would return to her own timeline, this was only the beginning of a love story for the two star-crossed characters.

Supergirl doesn't have many romances in the comic books, but her ongoing connection to Brainiac 5 is one of the most enduring ones, and it's one that many fans have latched onto. For that reason, the prospect of seeing Brainiac 5 arrive on the Supergirl television series makes us wonder if Kara is about to have a new love interest, especially now that Mon-El has moved on.