SPOILER ALERT! Spoilers ahead for multiple DC Comics and “Supergirl” stories.

In the November 14th episode of the CW’s “Supergirl”, National City’s burgeoning superhero pantheon gains another member, when Jimmy Olsen takes up the mantle of Guardian. A shield-slinging mystery man who first debuted in comics in 1942, Guardian joins an elite company of heroes that also includes the Martian Manhunter, Mon-El and Ms. Martian.

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With a long, rich history in the DC Universe, the addition of Guardian to “Supergirl’s” cast opens up several intriguing plotlines stemming from his connections to both the mysterious Cadmus organization and comics’ Golden Age. Over the years, several people have carried Guardian’s signature golden shield, adding new layers of complexity to the hero’s back story.

It’s not clear which version of the character Jimmy Olsen’s Guardian will draw upon, so we thought it was a good time to run down a list of 15 things you need to know about DC’s gilded mystery man.

15 Golden Age Debut

Like many mystery men born during the Golden Age of Comics, Jim Harper was an orphan, who grew up alone, only discovering the hero within after a childhood spent as a petty criminal. Jim lived off the streets in Metropolis’ notorious Suicide Slum and might have headed down a much darker road, if it weren’t for a man named Nat Milligan. Quickly identifying Jim’s fighting spirit and kind heart, Milligan takes the young punk under his wing and trains him in the sweet science of boxing.

Although Jim appreciated Milligan’s training, he wanted to give back to his community and returned to Suicide Slum as a beat cop, trying clean up his old neighborhood, with the help of the misfits in the Newsboy Legion. It’s a story that could only come from the Golden Age and harkens back to a time when comics were a little brighter and more positive in tone than much of our modern fare. Even more than Bucky or Robin, readers could identify with the Newsboy Legion, imagining themselves in their shoes, helping a superhero clean up the streets of his community.

14 A Simon-Kirby Creation

Guardian debuted a full year after the first appearance of Captain America, a slightly more prominent shield-slinger over at Timely Comics. Both characters were created by the legendary team of Joe Simon and Jack Kirby, who were responsible for the creation of dozens – if not hundreds – of comic book heroes and villains over the course of their respective careers. Jim Harper fits the typical mold of early Simon-Kirby collaborations. He was a non-powered, two-fisted fighter with a heart of gold, who more often than not, relied on his wits and his grit to win the day.

After decades languishing on the back burner, Kirby revived Guardian during his classic run on “Superman’s Pal, Jimmy Olsen”, a series that would also help launch his cosmic epic “The Fourth World”. It’s this historical link between Jim Harper and Jimmy Olsen that seems to have inspired “Supergirl’s” producers to pass the shield to Mehcad Brooks’ James Olsen. It’s a clever bit of streamlining that opens up a myriad of exciting storytelling possibilities for National City’s newest superhero.

13 He Was a Cop

One of Jim Harper’s defining traits is that he never stops being Guardian. Even out of costume, he walked one of the roughest beats in Metropolis, patrolling the streets of his home in Suicide Slum. Not only did his day job underscore Guardian’s virtues, his position as a beat cop provided near-infinite plotlines for the creative team. Protecting his community and meting out his brand of bare-knuckled justice to criminals wasn’t just a choice for Harper. It was his calling.

Jim’s inspiration to become a police officer emerged, when his childhood friend and former partner in crime was murdered in retaliation for his hit on a rival crime boss. Desperate to prevent more unnecessary deaths, Jim became a police officer dedicated to providing a positive example to local youth. He even used his status as a respected police officer to secure guardianship of the Newsboy Legion, setting them on a much safer path.

12 The Newsboy Legion

One of the more interesting facts about the original Guardian is that he wasn’t even the headliner of his own comic strip. His plucky sidekicks, a ragtag assemblage of newsies, who ran the streets of Suicide Slum, were the true stars of the strip, each feature story labelled with some variation of “The Newsboy Legion featuring the Guardian.” Each member of the Newsboy Legion embodied a different defining trait: Big Words was the team genius, Gabby was a rambunctious non-stop talker, Tommy was the indefatigable leader and Scrappy was the resident tough guy, who never turned down a chance to chuck the knuckles.

The Newsboy Legion’s legacy lived on through their identical sons – later retconned as clones – who all became scientists for what would eventually become Project Cadmus. There, they would eventually use the mysterious organization’s vast scientific resources to explore the field of advanced human cloning – an initiative that would not only produce a new Guardian using Jim Harper’s DNA but also a popular incarnation of Superboy.

11 He Was Trained by Legendary Boxer Joe Morgan

Unbeknownst to Guardian, the man who pulled him off the streets and trained him in boxing wasn’t who appeared to be. Nat Milligan’s real name was Joe Morgan, renowned prize fighter, who also trained Guardian’s fellow Golden Age mystery men Wildcat and the Atom. Thanks to some convenient retconning by “All-Star Squadron” writer Roy Thomas, Guardian had his first team-up with other mystery men on his first night in costume.

After busting up a pool hall full of criminals, Harper literally strutted around a corner and was teleported to a strange circus, where he was forced under brainwashing to fight members of the JSA. The man controlling Guardian and several other heroes was none other than the man Harper new as Nat Milligan. Learning his mentor’s true identity, Guardian and the JSA fought off Morgan’s programming and in turn freed him from the mental control of a vaguely defined malevolent presence known only as “Evil”.

10 That Funky Shield

Although it may not have the same legendary durability or remarkable versatility as Captain America’s famous disk, Guardian’s shield is still an exceptionally effective, if oddly-shaped weapon. The shield was a prop, found in the same costume store, where Jim Harper selected his signature blue and gold duds. Despite its mundane origins, the shield was virtually indestructible, even during Guardian’s early adventures. It wasn’t totally impervious to damage though, having been cracked or broken several times during particularly intense battles.

Over the years, the shield has enjoyed numerous upgrades, especially during Guardian’s time as Project Cadmus chief of security. It’s most noticeable enhancement in the modern age are anti-gravitational properties that allow the shield to double as Guardian’s personal hovercraft. Innovative functionality is all fine and dandy but the shield’s ultimate value may just come by way of that odd shape and brilliant golden hue, allowing readers to instantly recognize the hero, even in silhouette. Without it, the Guardian becomes just another costumed hero who wears his underwear on the outside.

9 He’s an All-Star

The classic ‘80s series “All-Star Squadron” was the brainchild of Roy Thomas, a student of comics history, who wanted to tell stories set against the backdrop of World War II, during comics’ Golden Age. It was an era Thomas was passionate about, having already produced “The Invaders” for Marvel, itself an excellent example of his use of retroactive continuity. The All-Star Squadron was formed at the behest of President Franklin Delano Roosevelt after the bombing of Pearl Harbour. Although the Justice Society was active at the time, it was a civilian entity lacking the structure of a dedicated wartime unit under federal authority.

Considered a reservist for much of the team’s existence, Guardian was a member of the elite group and thanks to some clever retconning, even met members of the Justice Society of America on his first night in costume. He later appeared in the massive gathering of virtually every Golden Age DC character in the now-classic “All-Star Squadron” #31.

8 Project Cadmus

The clandestine government project known as Project Cadmus originally went by the much plainer and revealing name of the DNA Project, in the pages of “Superman’s Pal, Jimmy Olsen”, during Kirby’s epic run. Under the guidance of the scientifically-gifted descendants of the Newsboy Legion, Project Cadmus as it would come to be called, cloned the original Jim Harper, hoping to leverage his DNA into a new Guardian. Project Cadmus was also responsible for the creating the second Superboy, from the cloned genetic material of both Superman and his arch-nemesis Lex Luthor.

On the CW’s “Supergirl”, Cadmus is a militaristic, scientific research unit, so top secret even the DEO didn’t know about it for years. Tasked with weaponizing extra-terrestrial technology and policing Earth’s alien refugee population, Cadmus has shown absolutely no regard for civil liberties, human or otherwise. Fronted by over-zealous xenophobes such as the enigmatic Doctor and a fanatical version of Jim Harper, Cadmus lurks at the center of many ongoing plotlines, including the final fate of Kara’s adopted father Jeremiah Danvers, the weaponization of Kryptonite in the form of Metallo and possibly the emergence of a new Guardian.

7 He’s Arsenal’s Great-Uncle

During his time working at Cadmus with Superboy, Jim Harper learns he is related to Roy Harper aka Arsenal, founding member of the Teen Titans and former sidekick of Green Arrow. As many comics fans know, Roy’s story has been one fraught with tragic loss, drug abuse and no little controversy. After losing his arm and his daughter to the villainous Prometheus, Roy descends into a cycle of self-destructive behavior that at one point sees him tripping out in an alley over a dead cat he believes is his late daughter – but the less said about that disturbing incident, the better.

In sunnier times, although Roy was unable to provide very much in the way of family history to Jim, having lost his father at a young age, the pair establishes a relationship that also included Roy’s ill-fated daughter Lian. In the years since this retconned relationship was established, it seems to have been undone by Flashpoint and the emergence of the New 52 DCU. Having said that, as DC’s Rebirth continues to unfold, including the reintroduction of the JSA, who knows what kind of connections will come to light about the Harper clan.

6 The Mon-El Connection

Due to his ties to both Superman and the Legion of Super-Heroes, Mon-El’s history is one of the most heavily retconned in the DC Universe. In the most recent version of his origin, Mon-El is a human-Daxamite hybrid who traveled to Earth in order to escape an increasingly xenophobic Daxam and explore his Terran heritage. His ship crash lands near Smallville, where he encounters a young Clark Kent, who believing he’s met a fellow Kryptonian survivor, promptly gives Mon-El lead poisoning. In order to save his life, Clark transports Mon-El to the Phantom Zone, until an antidote for his condition can be created.

He’s eventually released from the Phantom Zone and for a time is cured of his lead allergy. Jim Harper gives him a job with the Science Police, where he meets Harper’s grand-niece Billie, a special detective on the force. In the aftermath of the War of the Supermen storyline, it is revealed Billie is carrying Mon-El’s baby. With his recent introduction on “Supergirl”, Jim Harper’s affiliation with Cadmus, and a new Guardian on the horizon, it will be interesting to see what new connections between Mon-El and these seemingly unrelated characters will come to light.

5 He Was a Member of the JLA

In 2010, James Robinson introduced what was supposed to be a new, more proactive Justice League line-up that featured some rather peculiar members, including the Mikaal Tomas Starman, Congorilla and for about three seconds, Guardian. His first adventure with the team pitted him against Prometheus, who had invaded the JLA Watchtower, taking out several members of the League in the process. He accepted an offer of membership, participating in a battle with Doctor Impossible and his gang of evil New God duplicates.

Robinson’s run on JLA was ultimately short-lived, possibly due to the book’s lack of classic JLA members to anchor the team. Guardian’s tenure on DC’s premiere superhero team proved to be even shorter – Robinson wrote him out of the book after only three issues, in an effort to pare down the cast. Despite this brief stint with the JLA, in many ways Guardian was a perfect match for the group. Not only does his rich history in the DCU provide numerous potential storytelling outlets in a League setting, he also embodies the team’s values more than several of their past and current members, such as Green Arrow, who murdered Prometheus in cold blood.

4 He Saddled Up With The Original Vigilante

After the events of Infinite Crisis, Guardian’s back story was revamped and it was revealed in the pages of a new “Superman’s Pal, Jimmy Olsen” one-shot that the first Jim Harper clone created by Cadmus had escaped their clutches several years ago. It turns out Cadmus’s head of security Jonathan Drew murdered Jim Harper after he discovered this first clone already in development. The clone bailed on Cadmus, taking a young female clone named Gwen with him. The pair went on the run, until settling in the border-town of Warpath, NM.

Jimmy Olsen follows the leads of his investigation of Drew and Cadmus to Warpath, where he discovers a reborn Greg Saunders acting as the town’s sheriff. The original Vigilante refuses to reveal the clone’s location but Olsen tracks him down and learns Guardian’s many appearances over the years were in reality a series of unstable clones that all died one year after their creation. After helping Vigilante repel an invasion of villains from across the border, Guardian leaves Warpath for Metropolis in order to provide a stable home for Gwen.

3 Guardian II – Mal Duncan

Jim Harper and his clones weren’t the only heroes to pick up Guardian’s golden shield. Two other men would take up the mantle and perpetuate the character’s legacy in their own unique ways. Mal Duncan continued the Guardian legacy way back in 1977, in the pages of the “Teen Titans.” In addition to Guardian’s signature shield, Mal added a high-tech exoskeleton that enhanced his strength to superhuman levels. After taking out perennial Titans punching bag Dr. Light, he would go on to have many adventures with the titanic teens as Guardian.

Although Mal’s tour of duty as Guardian was retconned during “Crisis on Infinite Earths”, it is interesting to note that before his history was revamped, he met and saved the life of a Harper clone, who was being targeted by another, much more evil, duplicate named Adam. In a cool nod to his comic book roots, Mal also appeared as Guardian, alongside his traditional paramour Bumblebee, in a couple of seasons of the popular “Young Justice” animated series.

2 Jim Harper Already Knows Supergirl

That’s right, the live-action Jim Harper has already debuted on “Supergirl,” in last year’s “Manhunter” episode. Perhaps better remembered for revealing J’onn J’onzz’s back story, this episode also witnessed the introduction of the over-zealous alien-hater Colonel Jim Harper. Tasked with uncovering the circumstances surrounding DEO director Hank Henshaw’s death and subsequent impersonation by J’onn J’onzz, this version of Harper is shaping up to be much different than his comic book counterpart. Fueled by paranoia and blinded by his anger over his friend’s death, Harper is single-minded in his mission to see J’onn in captivity at Cadmus, where the Martian is destined for the dissection table.

Fortunately, thanks to the intervention of Supergirl and Lucy Lane, and with a little help from Alex Danvers, J’onn regains his freedom and control over his abilities. He telepathically erases the entire incident from Harper’s memory but not before learning that Jeremiah Danvers, Alex’s late father was, in fact alive and being held at Cadmus. It is unclear how deep into Cadmus Harper really is or if he’ll have any connection to James Olsen’s Guardian but it seems highly unlikely, given Harper’s comics origins that his introduction into the world of “Supergirl” was random.

1 The Manhattan Guardian – Jake Jordan

The next man to take up Jim Harper’s mantle was a former disgraced New York City police officer created by Grant Morrison, who takes a job as a local newspaper’s resident superhero/reporter. Jake Jordan was virtually unemployable after he mistakenly shot and killed a youngster on the job, until he accepted the position of the Manhattan Guardian. The paper’s publisher had purchased the superhero identity from Project Cadmus and intended to use his exploits to boost flagging circulation. Aided by a network of volunteer reporters called the Newsboy Army, Jake battled a gang of subway pirates, afterwards attempting to resign his position when the conflict results in the death of his girlfriend’s father.

The newspaper’s owner convinced him to stay on and help battle the other-dimensional Sheeda, who were eventually vanquished with the help of the second Mister Miracle, the Bulleteer and the rest of Morrison’s Seven Soldiers. Although this version of Guardian has yet to appear in recent continuity, there’s a very good chance that Jake Jordan is at least a partial inspiration for the James Olsen incarnation set to debut on “Supergirl” later this month.

What do you know about the Guardian that we don’t? Let us know in the comments!