[WARNING: There will be SPOILERS for the Supergirl TV series ahead.]

There may be comic fans who don’t know his name, but if you’ve followed an animated DC Comics property or comic book crossover events, you’ve seen the Martian Manhunter. The fact that he’s not as well known the world over as his colleague Superman, Batman or The Flash is just one bit of proof that he’s severely underrated in his own time. But that didn’t stop fans from wondering if the alien being known as J’onn J’onzz would be joining Zack Snyder’s big screen Justice League.

It seems that ship has sailed, but another has arrived in its place, with the green-skinned alien making his debut in the world of CBS’ Supergirl TV series. The show’s version of the hero is a bit of a departure from his classic origin, but there’s no doubt his arrival will get the diehard fans talking – and the casual viewers wondering what all the fuss is about. With that in mind, we thought it wise to lay out the essential bits of Martian Manhunter history, and explain why he makes the rest of DC’s biggest heroes seem like little league-ers trying to make it in the Majors.

Here is our list of 10 Things You Need to Know About Martian Manhunter.

He Was Introduced in ‘Detective Comics’ in 1955

Martian Manhunter Comic Origin Explained 10 Things You Need to Know About Martian Manhunter


As famous as the Martian Manhunter may be today, he came from surprisingly humble beginnings, making his debut in a backup story of “Detective Comics” #225 by Joseph Samachson and Joe Certa. No, not as a supporting character in a Batman tale, but as the accidental result of “The Strange Experiment of Dr. Erdel.” The doctor in question was trying to build a cutting edge communications device, but built an interplanetary teleporter instead. When he turned it on, out popped the green-skinned Martian taken from his home and family against his will. So, what made him stay on Earth? Well, his appearance was a bit of a shock to Dr. Erdel (understandably), causing the elderly scientist to die on the spot.

As entertaining as it may be to imagine the entire origin story of a future Justice League legend being a complete accident played out over a few seconds (and then imagining it again, and again), the Martian didn’t dwell on his predicament. Instead, he figured his family would get to work on bringing him home, and began to focus instead on solving crimes under the disguise of John Jones, a detective in Middletown, USA.

He’s Considered The Last of His Race

Martian Manhunter Origin Brother Mars Plague 10 Things You Need to Know About Martian Manhunter


The Golden age origin of J’onn J’onzz was, like most dc superheroes introduced at the time, eventually updated into a far richer, more archetypal story. Early stories claimed he wads teleported away from friends and family, and even communicated with them back on Mars from time to time. But as the years went by, reboots and reimaginings made J’onn’s origin far more tragic: he was the last surviving Martian, and had been for some time, living in isolation on Mars until he was teleported to Earth. And it was only his twin brother, Ma’alefa’ak he had to blame.

Among his Martian society, nothing was more sacred than the race’s communal psychic community – when every member of the race is gifted with telepathy, a new level of culture, family, and oneness is to be expected. So when J’onn learned that his brother, a Manhunter (policeman) like him, was charged with the highest crime imaginable – mind rape – he did his best to defend him. But Ma’alefa’ak was found guilty, and his punishment was severe: he was be stripped of his psychic powers, and have his memory of every possessing them erased. Filled with rage, he aimed high with his revenge, determined to kill each and every Martian who possessed the skills he did not.

Martian Manhunter Facts Fire Weakness 10 Things You Need to Know About Martian Manhunter


His answer was a plague passed telepathically, causing every Martian to burst into flames when trying to use their powers. Ma’alefa’ak figured he would be the only one immune, but his twin brother J’onn survived – his wife and children, however, did not. The two did battle and believed eachother dead, leaving J’onn with nothing but memories of his family and people, until he was called to Earth. Other Martian survivors or criminals have cropped up since, but it doesn’t change the fact that J’onn is the last embodiment of Martian peace and honor.

Shapeshifting is His Specialty

Martian Manhunter Shapeshifter Dragon 10 Things You Need to Know About Martian Manhunter


We’ll get to the rest of J’onn’s superpowers soon – and there a lot of them – but the first one that most heroes or Villains are likely to encounter is his ability to shapeshift, taking on the appearance of whoever he desires. He originally took the human form of a dying detective to stop crime while hiding, but has since used the power to distract, mislead, or infiltrate countless organizations, including the Justice League. But the process is a bit more complicated than just “changing what he looks like”: J’onn, like all Green Martians, is able to not just change what he looks like, but modify his body on an even chemical level. That means that aside from the ability to disguise himself as any human being or animal to blend into a crowd or landscape, increase or decrease his body mass as need be, and even take a monstrous form, he can adapt his physiology to any environment.

Chase an enemy to a planet deadly to oxygen-breathing organisms? Fine, J’onn can modify his body chemistry to be fed by whatever element is most plentiful. His mind is the only real limit, since all Martian strength comes from their mental power and concentration. It’s this mental focus that Batman realized was more important in battle than even J’onn realized. According to Bats, Martian shapeshifting was used almost as a reflex, as constant analysis and dissection of an opponent’s fighting style meant J’onn’s body could react on the fly, forming the advantage needed.

He’s The Most Powerful Being on Earth

Martian Manhunter Most Powerful DC Hero 10 Things You Need to Know About Martian Manhunter


When we hinted that the ability to completely modify his physical form on a physiological level was just the tip of the iceberg, we weren’t kidding. In addition to that case of ‘Martian mind over matter,’ J’onn has almost every mental or psychic ability ever introduced in comics, including the skill to read minds, control minds, project illusions into minds, manipulating or reading memories, and knowledge transference from one brain to another. His mind-reading powers are so advanced, he has even opened his consciousness to every mind on planet Earth – at once.

He also is a telekinetic, granting him the gift of flight, as well as the option of controlling and moving objects mentally. From there, it’s simplest to say that he has every ability possessed by Superman: superstrength, invulnerability, X-ray vision, super-breath, and the ability to fire beams of energy out of his eyes.

Martian Manhunter Superpowers Heat Vision 10 Things You Need to Know About Martian Manhunter


If that wasn’t enough, add the ability to change his body’s density to phase through objects, become invisible, and in one case, regenerate his entire body from his severed head. Add in a keen detective instinct, and you can see why Batman considers him the Dark Knight and Man of Steel rolled into one – and why Superman has referred to him as “the most powerful being on Earth.”

White Martians Are His Sworn Enemies

Martian Manhunter White Enemies 10 Things You Need to Know About Martian Manhunter


J’onn J’onzz is considered the last survivor of his Martian race… but that doesn’t mean he’s the last surviving Martian. You see, the population of the planet Mars (prior to the plague) was divided into two groups: the Green Martians, and the White Martians. In the history of fantastic moral tales, the Green Martians were the wise, peace-loving society that stood opposed to the greedy, slave-owning White Martians. When each respective race cloned themselves to create a workforce for the planet Saturn (just go with us), the Greens considered these beings their equals – where the Whites considered them slaves worthy of cruelty.

That was just one reason why the two Martian societies came to civil war, with planet Earth being caught in the crossfire. But the Green Martians won the day, banishing their enemies to the Still Zone (which may or may not be the famous Phantom Zone from Superman‘s Kryptonian mythology). On look at a White Martian is all you need to see that they’re intended to be the villains in almost any encounter, and most comic stories play out that exact way.

Fire is His Only Weakness

Martian Manhunter Fire Weakness Origin 10 Things You Need to Know About Martian Manhunter


If you were wondering how anything could possibly harm a superhero who makes Superman’s power set seem lacking, there is, of course, one exception: fire. In the early days of the Martian Manhunter, fire was only effective against the alien hero when he was actually in his natural form (offering yet another reason to live in hiding). But it isn’t just that fire burns J’onn J’onzz, it disrupts the most pivotal weapon he has: his mind.

The comics would later explain that the aversion to fire wasn’t just one of self-preservation or a dislike of blisters. As the comics would later reveal, Mars wasn’t always populated by two different species, but one type of being who preceded both of them, known only as The Burning. These creatures were bathed in flame, hungering for more planets and peoples to conquer, and spread like a wildfire across the universe. The Guardians of the Universe – the same group of celestial beings who created the Green Lantern Corps – formed a permanent rift in the species (dividing them into Green and White), instilling a fear of fire to make sure they would never realize the extent of their power.

The result: when J’onn (or any Martian) is exposed to flame, the very core of their being is shaken, sending them into a mental panic that typically renders them unable to even hold a solid form, melting into pools of liquid. It’s a troubling explanation, but when J’onn accepted this fact, his weakness to everyday fire was ended once and for all.

His Green Arrow Team-Up Redefined ‘The Brave And The Bold’

Martian Manhunter Brave Bold Green Arrow 10 Things You Need to Know About Martian Manhunter


It should already be clear that J’onn J’onzz and Superman have a lot in common, from their origins, powers, and respective cultural histories. DC Comics put that fact to good use in the years that followed his creation, since the executives were concerned that using Superman in each and every “Justice League” issue or story – along with his own series – would run the risk of readers growing bored of the same old heroics. So it’s fair to describe his role as an ally or charter member of the Justice League as a Superman substitute in practical terms, using the same powers the Man of Steel probably would have in the same situation.

But the popularity of the Manhunter from Mars was hard to ignore, and even though he hadn’t yet earned a standalone series, he was teamed up Green Arrow for their own adventure, without DC’s famous faces helping sell copies. The adventure shared with Green Arrow (who, himself, was created as Batman substitute for the very same reasons) saw the two heroes track down a supervillain suspect, mind-controlled into doing battle before the job was done. It was a winning combination, and “The Brave and The Bold” would remain a team-up title for the remaining 149 issues (with Batman sadly taking the spotlight all to himself).

He Became a Key Member of The Justice League

Martian Manhunter Justice League Origin 10 Things You Need to Know About Martian Manhunter


J’onn J’onzz was no stranger to the Justice League before ever becoming a full-fledged member, but it wasn’t until 1987 that he finally got his time in the spotlight. Under writers Keith Giffen and J.M. DeMatteis, the slumping “Justice League of America” series was replaced with a brand new version of the team, with a greater emphasis on the sense of humor and quirky personalities modern comic readers would expect. The Martian Manhunter was there from the start of this “Justice League International,” taking on the role of the often confused, out of touch alien being for the zany supporting heroes to bounce off of (but also had the stated eccentricity of being particularly fond of Earth’s Oreo cookies). It was this comic series and its spinoff which updated his origin to the modern version, and cemented him as a founding League member.

In the DC Animated Universe, J’onn was an even more important and integral member of the team, as the one who actually formed the stars of the Justice League cartoon series into a single team. Reaching out to each member telepathically, J’onn would prove particularly skilled as the League’s Monitor, keeping watch over the planet and all its inhabitants from the Watchtower floating in Earth’s orbit. Who needs communicators when you have a telepathic Martian relaying order and information from one team member to another? His origins and powers would be tweaked from the comics version, but for those who grew up on the animated series, the Martian Manhunter is synonymous with the Justice League.

His ‘Martian’ Appearance isn’t Actually Martian

Martian Manhunter Alien Original Form 10 Things You Need to Know About Martian Manhunter


So if he has the ability to become any human being or animal he can imagine, but reverts back to his Martian form when fighting crime as himself, then that must be his ‘true’ form, right? Wrong. As much sense as that would make, the comic writers came up with a more complicated – but more interesting – explanation. When J’onn first appeared in Dr. Erdel’s laboratory, he modified his appearance into something of a compromise: he was still wearing traditional Martian clothing, but adjusted his appearance to something more humanoid, based on Dr. Erdel’s idea of what a Martian should look like. Thus was born, the bald, green-skinned, broad-chested Martian fans know and love.

But it is not J’onn’s true form – a fact that he’s been open about in nearly every comic series in which he’s appeared. The ‘real’ J’onn is up for debate, since he has occasionally admitted that even at home on Mars, his birth form was saved only for private (getting another glimpse at how a society would form when each member can look exactly how they want to). But to keep things simple, the birth form of a Green Martian is far more alien, with extended skulls, thinner bodies and limbs, and definitions of beauty less tailored to that of humans. Modern comics starring J’onn have stayed closer to this idea, wisely replacing his bare-chested, high-collared costume to something a bit sleeker.

Supergirl’s Version is Making Some Serious Changes

Supergirl TV Martian Manhunter Jonn Jonzz 10 Things You Need to Know About Martian Manhunter


As movie fans hoped to one day see a version of Martian Manhunter brought to life using modern special effects and prostethics, ideally in a big screen Justice League, the makers of CBS’ Supergirl series were developing their own version in secret. The overall design sticks fairly close to modern styling, but the origin story and alter ego concocted for the TV show kept fans completely in the dark. J’onn’s human disguise, Hank Henshaw, threw fans completely off the scent, since the character is already known as Cyborg Superman (a half-human, half-machine copy of the Man of Steel).

That blending of comic book characters may be seen as sacrilege by some, but the core of the character seems more faithful than not. J’onn came about his identity as Hank Henshaw in a similar way: with the real Henshaw being lost on a mission with Supergirl’s adoptive father Jeremiah Danvers in tow. J’onn J’onzz was their target, and Jeremiah ensured he wouldn’t be captured. It cost him his life, but J’onn emerged in Henshaw’s place, hiding in plain sight and working to keep humanity safe from all extraterrestrial threats. The names and details may have changed, but the overall effect is the same: as “the sole survivor of his planet,” this Martian Manhunter finds a new name and cause – now to see if Kara gets him in touch with her cousin Superman, or keeps his help all to herself.

We’re eager to see what CBS has up their sleeves for this new take on Martian Manhunter, or if Warner Bros.’ shared movie universe will find a role for J’onn J’onzz once their stories go cosmic. We hope that this list of essentials has given curious fans enough information to get excited about what may come next (and offered a quick reminder for lapsed Justice League fans). But with promises of a Martian Manhunter series woven through Supergirl, fan hopes have never been higher.

Next: Supergirl Team Discusses Martian Manhunter Reveal

Supergirl airs Mondays @8pm on CBS.