Martian Manhunter is a serious and level-headed voice of reason for the Justice League. He always speaks with politeness to his associates, both young and old, and has not shown any sign of anger or ego, although he can be stern at times.
He is caring and protective of his niece, Miss Martian, who he initially did not bring to the Hall of Justice to meet with the other young heroes. Eventually he changed his mind and introduced her to the Team. He later visited her at the Cave to see how she was doing, multiple times.
In 1955, J'onn J'onzz was transported from Mars to Earth due to a Zeta-Beam accident that took place during an experiment conducted by Dr. Erdel.Stranded on Earth for decades, J'onn became the hero Martian Manhunter. The Martian Manhunter became one of the seven founding members of the Justice League. He lives in an apartmentin Chicago.
In June 2010, he discovered a martian girl who claimed to be his niece, stowed away on his ship on a trip back from Mars.He decided to let her stay with him for the time being.Miss Martian is the daughter of J'onn's sister from an interracial marriage to a White Martian.
When Batman, Flash, Aquaman and Green Arrow decided it was time to take steps in which to induct their sidekicks Robin, Kid Flash, Aqualad and Speedy into the League, J'onn and Red Tornado were both present at their first visit to the Hall of Justice. He welcomed them inside and gave them a short tour, culminating in the library, and which point Speedy confronted the adult heroes about all the stuff that had been kept from them such as the orbiting satellite headquarters called the Watchtower. As Speedy stormed off, Green Arrow inquired if J'onn was glad that he didn't bring "you know who" along, which J'onn couldn't help but agree with.
After the sidekicks managed to defeat Blockbuster at Cadmus Labs, the League agreed that the kids had made an impressive team, and opted to turn them into the League's covert operative group. Seeing what the newly created Team had accomplished, J'onn decided it was time to introduce them to Miss Martian.
Some time later, J'onn paid a visit to the Team's base inside Mount Justice, where he greeted his niece very warmly, and proceeded to watch the Team's first combat training sessions with Black Canary, shortly before they were assigned a mission by Batman.
A few months later, he and Red Tornado helped Miss Martian and Superboy prepare for their first day of school. Martian Manhunter revealed that his Earth name was "John Jones", while Red Tornado went by John Smith", and suggested that Superboy might go by "John" as well. Superboy goes with "Conner", a name Miss Martian selected, and the last name "Kent", which Martian Manhunter suggested.
After the Injustice League attacked several world cities with mutated plant creatures, the Justice League responded in full force. Aquaman and Martian Manhunter took care of a plant that had completely covered the Eiffel tower. They got help from Icon and Rocket.
As part of the Team's training, Batman and Martian Manhunter devised a telepathic simulation that would teach them how to deal with an alien invasion after the League was killed in action. However, after Artemis was "killed" in the mission, Miss Martian's far superior mental powers took over the simulation. In order to regain control, he had to enter the illusion. But in the process, his mind was overwhelmed by the Team's emotional turmoil, and he could not remember why he entered. Only after all other members of the Team were killed could he get through to his niece. He "killed" her, so the telepathic trance would be lifted.
Mount Justice October 16, 16:21 EDT
He was shocked his niece possessed telepathic powers which, although crude, outmatched his own. He expressed his concerns to Batman, who had his hands full in consoling the Team after their traumatic experience.
Martian Manhunter and Batman kept close watch on the Team, who were still not fully recovered from the trauma. After Superboy ran off with the transformed Sphere and reported back, Martian Manhunter agreed with Batman that they should investigate Sphere.
Martian Manhunter fought alongside his niece at one of five flying ice fortresses that covered the United States with snow. He telekinetically destroys a defensive turret, before Zatanna brought the airship down.
Martian Manhunter was with Batman to ease Green Arrow and Black Canary after viewing surveillance footage of Canary apparently kissing Superboy. J'onn assured her it was a common game on Mars, and Conner likely knew it wasn't Black Canary. It did not fully satisfy Dinah.
Martian Manhunter took a vocal role in the discussion to admit more members to the Justice League. He feared that a larger League would spark opposing groups like the Injustice League. Superman offered him the opportunity to vote no on all candidates. After discussing Red Arrow's maturity, Martian Manhunter questioned age, as his niece was adult in human years, but not yet biologically. She was eventually added to the list of candidates.
After being made a slave of the Light's mind control, Martian Manhunter welcomed Vandal Savage aboard the Watchtower with a silent kneel of obedience. In the time he was enthralled, the Light used him and five other Leaguers to attack Rimbor. For sixteen hours, they went on a rampage, and told all present to beware the Justice League, and Earth.
When Black Canary, Red Tornado and Red Arrow came to the satellite and Klarion discovered they weren't under mind control, he summoned the six heroes that were on a mission back to the base. Martian Manhunter wanted to attack Red Arrow, but he was taken down by an incendiary arrow.
When the Team arrived, he fought his niece. Though he caught her trying to sneak up on him, she changed into her true form and placed him in a telepathic inferno. She then placed a cure-tech patch on him.
Martian Manhunter was one of several Justice League members who had responded to the emergency in Metropolis. He was unable to contact anyone inside the force field telepathically, nor could he density shift through the field.
Martian Manhunter decided to confront Metropolis's attacker. He levitated Flash and himself to the ship and hailed it verbally, telepathically and on all frequencies. They were backed up by a squad of Team members inside an invisible bubble generated by Zatanna.
Metropolis December 1, 17:45 EST
Martian Manhunter, the Flash, and Atom sneaked aboard the alien vessel, and were soon approached by the Collector of Worlds. Martian Manhunter telekinetically levitated the Collector, and attempted to disable him. However, the Collector's reinforced skeleton proved to be too powerful to dismember. Martian Manhunter and his team were eventually defeated by the Collector, and dropped, via a hatch, from the Collector's ship.
After Nightwing contacted Martian Manhunter that they were inside the ship, J'onn lifted Flash and Atom to safety.
Metropolis December 1, 19:03 EST
Martian Manhunter phased back aboard the ship, where those who had been on Kylstar's vessel had joined them. The original coludroid was destroyed, but dozens more coludroids showed up and surrounded the heroes. Nightwing and Atom persuaded the Collector to shut down the beam that shrunk the city.
Metropolis December 1, 22:03 EST
Back on the ground, Martian Manhunter discussed the double alien incursion with Captain Atom, Nightwing and the others.
After an attack by Lobo on a Krolotean in the UN building, the League and the Team convened a meeting how to deal with the matter. Martian Manhunter brought his friend Adam Strange along, who could supply them with plenty of information on the Kroloteans, and a related theft on Rann. The League and the Team were split up into several squads to deal with the Kroloteans on Earth.
Martian Manhunter interrogated a Krolotean captured by Robin, Blue Beetle and Lagoon Boy in New Orleans. He tried for days to work on the translation of the alien language, but could not get through. Miss Martian interrupted the interrogation and extracted the information of the Krolotean's mind, which left him comatose.
South Pacific January 6, 20:32 HAST
Martian Manhunter and Miss Martian broke in the Krolotean base on Malina Island, disguised as Kroloteans. While the Justice League and the Team were discovered by the Manta Troopers and the Kroloteans, they stole a data disk containing schematics of the Kroloteans and escaped the base.
They entered the Bio-Ship and waited until the Team and the Justice League evacuated the base, before the bomb went off. They flew away in the ship, nearly being engulfed in the explosion.
Martian Manhunter and the other accused Leaguers had to leave for Rimbor to stand trial for their actions under the Light's mind control. Martian Manhunter said goodbye to Miss Martian, and asked her to water the plants at his apartment.
L-Ron showcased an image of Martian Manhunter to Despero, as one of Earth's most powerful beings that could challenged for a match. However, he moved on to other prospect contenders, due to Martian Manhunter's absence from the planet.
Martian Manhunter watched on as Superman pleaded his case to the Tribune. When the trial was interrupted by a message that the Reach was on Earth, John Stewart explained their history to Martian Manhunter.
Rimbor June 20, 00:16 UTC
Manhunter and the other Leaguers were found guilty of all charges and taken away. Superboy, Miss Martian and Adam Strange arrived in court, presented new evidence and argued the Tribunal should reverse its decision. After further deliberation, the charges against J'onn and the Leaguers were dropped and they were released from custody.
Rimbor June 20, post-00:16 UTC
As Manhunter and the other Leaguers walked the streets of Rimbor, ready to return to Earth, Vandal Savage broadcast a message through holographic monitors, declaring Earth off limits to alien invasion. Superman was skeptical about Savage's threat, but then Batman pointed to a giant satellite, the Warworld, passing through Rimbor.
The League finally arrived at Mount Justice, J'onn among them. The mountain was in ruins, and Superman wondered whether they were already too late in dealing with the invasion that embroiled the Earth before and during their absence. Members of the Team descended from the heavens, acting as a welcoming committee. Batman asked Aqualad, who in their last meeting was still a traitor, what happened there. Aqualad reassured them that the crisis has passed, but not without loss.
When the Team was summoned to the mission room for a face-to-face meeting with members of the League, Martian Manhunter was among the leaguers present. Batman informed them that they would now operate side-by-side with the Justice League from the Watchtower. Not because Mount Justice was destroyed, but because they earned the right to do so. The League then left the Team to its own devices.
Young Justice marks J'onn's sixth animated incarnation. He has previously appeared in the DCAU (Justice League, Static Shock, and Justice League Unlimited), The Batman, Batman: Brave and the Bold, and in the DC animated moviesJustice League: The New Frontier and Justice League: Crisis on Two Earths.
In the comics, J'onn is not related to Miss Martian, due to the fact she is a White Martian, rather than a Green Martian.
The costume that J'onn wears in the show is actually the second costume he wore in the comics. It was also the costume that J'onn died in, early on during the company-wide series Final Crisis (J'onn was brought back to life during the Blackest Night crossover).