"Metamorphosis" is composed of the twenty-second and twenty-third episodes of Justice League. It first aired on October 4 and 11, 2002.
Simon Stagg shows a group of investors footage of a recent industrial accident suffered at one of their oil rigs and says he has the perfect solution: "Metamorpho," a genetically mutated human able to survive under hostile conditions. Stagg says he has perfected the theory and is only awaiting a human subject to test it on. The investors are skeptical and demand proof.
Aboard a commuter train, Stagg's henchman, Java, is carrying a briefcase of mutagenic chemicals toward the city, which Stagg tells him not to let out of his sight. But as soon as Java hangs up, an attendant tells him that personal luggage isn't allowed and he'll have to stow it. Confused, Java surrenders the briefcase, and it's placed in the luggage compartment. Before long, the train's vibrations spill the chemicals inside, and the reaction with the train's hull causes it to derail. Green Lantern arrives to minimize the crash.
While examining the train, a familiar voice hails him, and is surprised to see his old Marine Corps comrade Rex Mason. Mason says he is now a high-placed executive with Stagg Enterprises and was a passenger on the train.
Rex invites John back to his apartment for a drink. John is a little taken aback by his friend's luxurious rooftop apartment and even more taken aback to meet Rex's lovely fiancée, Sapphire Stagg. Rex says they are in love, though they have kept their relationship secret from Simon.
While they are talking, John receives a call from Batman, who was investigating the crash and has discovered traces of the mutagen. John confronts Rex, who claims ignorance, and the two men part on a sour note.
Rex confronts Simon, who tells him not to worry. Rex is angry because the chemicals Java was carrying are illegal, and Simon expects him to shut up about it. He informs Simon that he's decided to quit Stagg Enterprises and take a job in another city. Later, when Simon pays a surprise visit to his daughter's apartment, he is surprised to find Rex there. She tells her father that she is going to go with Rex. Simon pretends acceptance but is furious.
The next night, while Rex clears out his desk, a security alarm sounds from a science lab, and security doesn't answer his call. He goes down to investigate himself and gets lured into a chamber where he is doused with the mutagen. When Rex regains consciousness in a hospital bed, Simon and Sapphire are standing over him, looking horrified. He looks in the mirror and sees himself transformed into a multicolored mutant. Screaming, he rushes out into the night.
Out on the street, he wanders in front of a truck and is splattered all over it. To the police and the driver's shock, the splattered remains reform into Mason. The alarmed police open fire, and the bullets bounce off his body like rubber.
Lantern follows the reports to the accident site, where Stagg, Java, and Sapphire listen to the police give their report. Sapphire begs John to find Rex before the police do, and he promises. While taking pictures, Java snaps a shot that makes it seem as though she and John are embracing.
Simon returns to his office and finds Mason sitting at his desk, having reviewed his project files on "Metamorpho" and realized that what happened was no accident. Mason demands the truth, but Simon distracts him with the photo, tricking Mason into believing that John has stolen his girlfriend behind his back.
John enlists the rest of the League to track down Mason. They are interrupted by a bank robbery. As they pursue the robbers, Lantern easily stops the truck and disables two of the robbers, but misses a third, and Hawkgirl has to intervene before John is shot in the back. John admits that he's distracted, confessing to her that he's having misgivings about the choices he's made; had he taken a different path, he might be where Rex is now. Then Rex calls him, saying they need to meet.
John flies to meet him at a chemical plant owned by Stagg. As soon as he arrives, Rex attacks, now believing that his old friend has betrayed him. Against the full range of Mason's new powers – the ability to mimic any chemical reaction – John is helpless and knocked unconscious.
As Rex prepares to kill John, the rest of the League arrives and fights him, but he fights off all of them by using their weaknesses, Superman when he transforms a piece of his arm to emit Kryptonite radiation and J'onn J'onzz by blasting him with fire. As the battle goes on, Simon and Java sit in a nearby van, filming the whole thing.
Eventually, Rex decides to run and slips away. He returns to Sapphire and angrily confronts her about her "affair." Shocked and angry, she tells him he's been fooled and that she still loves him despite whatever he's become. Realizing that Simon has played him, Rex rushes out again.
Simon shows his investors the footage of "Metamorpho" battling the Justice League, and they are now eager to buy. Simon confides to Java that now that he has proven the process, he can create a better Metamorpho and doesn't need Mason anymore. Mason arrives in time to hear this and is ready to kill Simon, but Java stops him by spraying him with liquid nitrogen, freezing him solid.
Sapphire calls John and tells him the latest. John reassures her and is surprised to hear that Rex has followed his career avidly and even been jealous of him – the selfless hero.
Two of Simon's thugs plan to dump the frozen Mason somewhere, but he thaws out first and escapes the truck. He rushes to the Stagg Enterprises lab, where Simon is preparing a fresh batch of the mutagen with a virtual reality control device wired to a headset. Mason swears that Simon won't do the same thing to another person and smashes the controls while his headset is still wired into the chemicals. The feedback causes Simon to scream and collapse, and to Mason's shock, the chemicals come to life, forming a huge, lumbering monster.
John and Batman arrive at the lab site, finding both Stagg and Mason. Mason apologizes for his earlier rampage and says they need his help. Lantern flies off with him, while Batman stays behind to analyze the chemical residue.
In downtown Metropolis Superman, Hawkgirl, and J'onn J'onzz try to stop the creature, but it is too resilient. When Lantern and Mason arrive, they share what they know, and J'onn says that he sensed a limited, primal intelligence within the creature. Mason theorizes that the monster has absorbed a part of Simon's mind, meaning he is acting on Simon's desires—and becomes horrified when he realizes what the monster is after.
In their apartment, Sapphire is watching the news of a colossal creature defeating the Justice League. Then the creature itself arrives, grabs her, and starts climbing up the side of a tall skyscraper. The entire League plus Mason tries to rescue her, but the creature is still too tough.
Then Batman calls, saying he's analyzed the formula and that they can destroy it using a designer amino acid – the problem is, it'll take days to make enough of it. Mason proposes a radical alternative: he can morph his body into the acid and combine himself with the creature. When Lantern objects that would be suicide, Mason gasses him unconscious, saying they don't have time to argue.
Rex climbs up the building and confronts the creature, telling it to let Sapphire go. Taking on Simon's face, it refuses. With a last "I love you" to Sapphire, Rex morphs into the amino acid, dives down the creature's throat, and the acid blossoms outward. In his hospital bed, Stagg bolts upright, screaming.
As the creature writhes, it drops Sapphire. John wakes up just in time to see her fall and catches her, and they watch as the creature explodes. Seeing nothing left of the creature or Rex except dregs, Sapphire sobs against John's shoulder.
The League assembles on the apartment's balcony to console Sapphire, and John says Rex was a true hero. As Sapphire cries, one of her tears falls into a puddle of the chemical, which begins to rise from the ground. To the others' amazement, it resolves itself into Rex, alive but not unscathed. ("Wouldn't want to do that again.")
As Sapphire throws herself into his arms, Hawkgirl winks at John, asking, "Still regretting the road not taken?" Seeing the happy couple, John replies, "What do you think?"
- In "Hereafter," John proposes Metamorpho as a new member of the League, to replace the apparently fallen Superman. In Justice League Unlimited, "Initiation," Metamorpho is indeed shown as a member of the expanded League.
- In Justice League Unlimited, "The Once and Future Thing Part Two: Time, Warped," Warhawk (last seen in Batman Beyond, "The Call,") reveals himself as John's son, Rex Stewart, a strong indicator that he is named after Mason.
Home video releases
- Justice League - Season One (DVD)
- Justice League - The Complete Series (DVD)
- Justice League - Season One (Blu-ray)
- Wonder Woman and Flash do not appear.
- The climactic scene is an obvious visual parody of King Kong. While climbing up the side of the building, Metamorpho quips, "What I wouldn't give for a couple of bi-planes right about now."
- The climax's premise, a monstrous creature created by a man's subconscious desires, especially his selfish attachment to his daughter, is likewise used in the classic 1955 science fiction film Forbidden Planet.
- The Synthoid bears a strong resemblance to Chemo, a chemically based monster that has threatened the world on several occasions.
- Rex calls Java "Flintstone," referencing the famous Hanna-Barbera cartoon series Flintstones.
- Mason's apartment reuses the backgrounds of the apartment of Warren Lawford from the Batman: The Animated Series episode "The Terrible Trio"
- In Part II, Hawkgirl throws her mace at Stagg-creature, who swallows it and spits it out several feet behind her. Then, he grabs Hawkgirl and slams her against a building's wall, and she falls unconscious on the top of a car below. In the next scene, when she comes to, her mace is strapped around her wrist.
- In Part II, right when Rex begins to reform himself after destroying the Stagg monster, Hawkgirl wears heeled boots, while her regular character model has flat sole shoes.
- In Part II, after Java freezes Metamorpho, Simon Stagg knocks on Metamorpho's frozen face, but the sound of the knocking is only heard after Stagg lowers his hand.
Train attendant (uncredited)
|Phil LaMarr||Green Lantern|
Truck driver (uncredited)
Stagg thug (uncredited)
|Carl Lumbly||J'onn J'onzz|
|Tom Sizemore||Rex Mason/Metamorpho|
|Earl Boen||Simon Stagg|
|Danica McKellar||Sapphire Stagg|
|Michael Bell||NTSB Inspector|
|Jason Marsden||Snapper Carr|
Rex Mason: Working for an outfit like Stagg Enterprises does have its perks...
John Stewart: I've never thought much about the choices I've made. Maybe if I'd taken the other road, I'd be where Mason is now. Rich, successful...
Sapphire Stagg: No wonder he always looked up to you.