Snake (human) Leonardo AU:
This probably won't make sense without reading the original story: https://archiveofourown.org/works/14209308/chapters/32755569
Practically everything unfolds exactly as in the SunnyLighter's story, 'Same Difference.' The changes begin in the chapter 'A Mother's Love'—or rather, 'A Brother's Love' here—with Miwa hanging in a cage above the mutagen, and Leonardo atop the vat, trying to save his sister when Shredder catches him. And here comes the first key change: Saki decides that 'Raion' is too similar to Yoshi. This time, he doesn't try to stab him. He simply throws the boy into the mutagen. Very effective 'adoptive parenting'.
Leonardo falls into the substance (less drama and slowmotion than other versions), along with all his weapons. He mutates and partially fuses with the metal. Shredder jumps from the vat to the ground. It's no longer his problem. Tang Shen destroys the Footbot attacking her and frees Miwa from the cage. Then she does notice that her son has disappeared. Normally, that's not a good sign near the mutagen.
Leonardo leaps out of the tank. He looks similar to Medusa-Shen in the main story, but with a few original changes:
His skin is now white scales, and his legs merge into a tail. His facial features remain almost unchanged. His eyes are venomous green with dark blue irises and vertical pupils. His hands appear essentially normal—aside from the scales and metal claws. The tip of his tail is a fused kunai. His katana blades extend from his elbows, as integral to his body as his bones in this form. The scales around his eyes are blue (reminiscent of Leonardo's bandana from the series). The most shocking change is his hair. Unlike Shen's, his hair is also a nest of black snakes with dark blue shine, but they sleep and remain coiled. As a human, his hair is significantly shorter than his mother's, so clearly even the mutagen has budget constraints. He still wears the upper part of his shinobi shozoku; the lower part is severely frayed.
Another major difference between him and the series' Karai and the story's Shen is that he immediately attacks Shredder. Unlike them, he didn't fall into the mutagen accidentally—he was thrown there, remembering it, and remembering the perpetrator, even in his feral state. He attacks the enemy to protect his family, so when a fire breaks out, Shredder and his subordinates retreat from the warehouse. They know that the Hamato family, especially Yoshi, will suffer. And also that a burning warehouse with an armed, hostile mutant snake is Saki's future problem.
Leonardo sees his reflection in the glass of the tank. He tries to escape, but Raph and Miwa successfully block him. He avoids them, and then Mikey hugs him. He tells his older brother he's not afraid of him. The roof begins to collapse, and Donnie is about to die in the rubble before Leo quickly carries him out of the building. By the time the rest of the Hamato family reaches the outside, he mostly transformes back into a human. He retains his fangs, snake-like eyes, and translucent scales. A less visible change is his slightly curly hair, still vaguely reminiscent of snakes. His clothing is undamaged.
Ask the show's creators; a specific example: Karai.
Donnie nervously explains how the ships in Space Heroes work, and his brother seems to actually listen. Eventually, his parents convince him to come home with them.
Leonardo sets up a nest in the basement, hisses even at his family, and tells April and Casey to stay away. In moments of clarity, he speaks (quotes below the fanart), sometimes drawing out the 's,' sometimes not—depending on how much his body currently resembles a reptile. April, however, doesn't listen and tries to 'awaken' his human side and get rid of his snake side, a bit like with Splinter in Season 3.
Initially, it works as well as therapeutic conversation with a brick.
The reluctant Miwa and Raph share command. Mikey comes to visit his brother, tells him Space Heroes plot, episode by episode, and brings photos. Raph tries to provoke him into a fight so things can go back to normal. Casey talks about hockey and school. Well, mostly hockey. Miwa generally avoids the basement, feeling guilty. April tries to 'wake him up' every day, and Shen brings food and blankets.
Lots of blankets. Three people in this family are now reptiles. It's winter. Shen thinks practically.
Finally, Yoshi teams up with April. He uses the Healing Hands, and she finally reaches Leo in his mind. Finally, some progress. Their joint rehearsals last about a week. Meanwhile, Donnie works on the Turtle Mech, on anti-mutagen and plans for a Leo-less Invasion.
Nothing says 'I can handle stress' better than building a giant war mech.
After more than a week of April and Yoshi working together, Leo regains a good portion of his mental clarity, though still not all of it. He cautiously exits the basement—until he bumps into his siblings watching 'Super Robo Mecha Force Five.' Mikey simply says:
And then everyone realizes he's out and calm.
And they just sit there in complete shock.
He tries to maintain his human form as long as possible. He trains with Raph during Donnie and April's date (kind of like their training session from Season 1 episode 1 of the show), and reluctantly stays home with his parents later. Leatherhead arrives while Leo is meditating with Yoshi and Shen. Together, they go to help the others.
Shredder forms an alliance with the Kraang, wanting to control the city and kidnap and demutant Mikey and Raph to use them as bait for Shen.
Hamato family's problems remain the most dangerous thing in New York.
Because of the explosion, Raph separates from the others. The Footbots lead him to a construction site. The fight turns out to be more of a test of his combat skills and a way to tire him out before being kidnapped than a real threat. However, his body continues to cool down, almost to the point of unconsciousness. He desperately wants revenge on Shredder for what happened to Leo. Hypothermia saw this as the perfect moment to intervene.
Then his parents and Leo appear. They save Raph from being kidnapped, and Shen immediately wraps him in blankets. She brought them from home because, again: three reptilian mutants in a family, winter, New York. She has experience now. Leo carries his brother to April's house. Raph is delirious from exhaustion and cold, speaking completely nonsense.
'Warm. I understand now. Sorry.'
Raph falls asleep, this time for real. Not for a moment, but completely succumbing to his turtle instincts. They wait. Finally, Shen says they need to leave the city and better prepare, because the situation has reached 'Shredder is working with aliens against our family' level. Again.
They escape from the Foot clan and Kraang Prime. Near the construction site, Shen, Casey, and Metalhead remain in the van with Raphael, while the teenagers run to the sewers. They see Shredder and Yoshi fighting. They see the knockout blow. Shredder throws Yoshi into the water, and Leo willingly transforms into a snake, squeezing through the grate and jumping in after his father. Being a terrifying snake mutant sometimes proves quite practical.
The rest of the main cast later meet up in a van and escape to the countryside (it's much warmer there; after all, in the series, they spent the entire winter there as turtles without any problem). The children are shocked. Raphael fully awakens after a week (they warmed him up in time to avoid a coma) and immediately wants to return to the city. However, no one is able to. Miwa continues training with frustration and aggression, and Raph quickly joins her. There's now a gap in the sibling order, specifically between them. They also have to try to replace their leader together. In the end, the fact that the entire group tells each other stories about Leo and Yoshi helps them.
Meanwhile, in New York: Yoshi doesn't wake up for several days. Leo practically stays with his father for most of that time. After seeing Shredder, his residual snake instincts take over again. It's not because he's losing his mind—it's just that his body perceives Saki as a direct threat to the family and reacts exactly as the trauma and the mutagen have programmed it.
He spends most of his time in mutant form, gathering supplies, medicine, and guarding his father. The Footbots quickly discover that a 'giant white snake with katanas' is a particularly effective argument for a job change. One night, Leo encounters the Mutanimals. They form a temporary alliance—until the Hamatos return. Together, they rescue people from the city, gather survivors in the sewers (including Casey's father and sister), and create a shelter. Slash leads most of the combat operations, and Leo becomes a medic. Slowly, their mutual hostility turns to tolerance, and then even a sarcastic friendship. When Yoshi awakens, he begins teaching Leo the Healing Hands.
Even a partially feral Leo still reacts to the wounded with his first instinct: 'Sit down and let me disinfect your wound.'
At the farm, Shen quickly resumes her training schedule. She adds meditation and long-range weapons to the children. Two months after Raph's awakening, she sends her children on a Vision Quest into the forest. April, Casey, and Metalhead organize a sleepover in a tent and a bonfire during this time.
One group undergoes spiritual warfare therapy.
The other roasts marshmallows.
After another episode of 'wild snake state' during a supply run and a fight with footbots, Leo has had enough. He decides to try to regain complete control of himself and goes to meditate. He opens his eyes in the forest next to his siblings. They all see each other for the first time in months.
All of them just gets watery eyes randomly.
Then the mist separates them.
Each finds themselves alone in a different area and facing a different opponent. Miwa fights the show's version of Karai, Donnie fights Tiger Claw, Raph fights Fish Face, Mikey fights Rahzar, and Leo fights... his own snake form.
At first, he looks like a perfect predatory version of himself—a giant white mutant with green and blue eyes and katanas at his elbows. Then he starts saying things Leo truly fears. That his mutation saved him. That he's stronger in this form. That his family needed this very thing to survive.
Spiritual visions are still an exceptionally brutal form of therapy.
Leo tries to fight. Of course.
It doesn't work. Of course.
Finally, the Shredder appears.
And then Leo stops fighting the snake.
Because, no matter what, they both hate the same man.
The snake attacks Saki first, Leo a second later. They fight together—instinct and human, mutant and boy, two parts of the same person.
It is The vision-Shredder who kills Leo's snake form. He pierces and tears it apart during the fight, wanting to get rid of the 'monster' he created.
And then Leo kills The vision-Shredder.
He accepts his mutant abilities and this new part of himself.
The snake disappears peacefully. Not like a monster. Like a part of him that simply wanted to protect his family as best it could.
After the fights, the siblings see each other again. Leo takes on his full human form, though his hair is still slightly curly. Raph teases him a bit about this. They all promise each other that they'll see each other again soon. This time, in real life.
Leo returns to his body in New York with the understanding that his mutation was never a separate entity. It wasn't a parasite or a curse. It was an exaggerated, twisted protective instinct.
The mutagen simply turned his trauma into a biological problem.
The Hamatos, April, Metalhead, and Casey return to the city about a week later. The Mutanimals find them in the sewers and lead them to The Shelter. There, they find a medical station full of newly arrived wounded and a very familiar manager.
'Did you hear that?! He told us to bring medicine!' Slash yells across the sewers.
Raph looks at Leo with a deadly gaze.
'You couldn't go a few weeks without commanding people.'
'Leo, you're running an underground hospital.'
During their reunion, Casey takes a selfie with all the teenagers and Metalhead. Later, during the Hamato siblings' time travel, April and he disappear into that very photo.
Meanwhile, the Shredder receives reports and recordings. He decides Leonardo could be useful as a weapon, a soldier, or bait for the rest of the family.
Renet subplot. During time travel, they find themselves in 1990s Japan, a few years before Miwa and the boys were born. Hamato Yuuta sees the transformation of the snake 'Raion' into a human. Later, he simply invites the children over for food.
Which says a lot about the Hamato family.
Sitting at the table, Yuuta begins to notice similarities. Mikey's mannerisms are reminiscent of Yoshi. Miwa looks like Tang Shen. Leo has their facial features and politeness.
Yuuta begins to have very serious suspicions.
Then he asks: Are you a shirohebi, young Raion?
Raph: Yes. And we are kappa. Along with these completely random people, we bring a warning, like in the myths, against Oroku Saki. And we are definitely not siblings. Neither your grandchildren.
Yuuta: Young Iyasa's words seem justified 🤔.
Back in the present, Donnie demutates Raph and Mikey. Then he begins experiments to find a cure for Leo.
At best, the mutation ignores the anti-mutagen.
At worst, something explodes. The worst cases happen every other day. Leo's tired of explosions so close to his face. He even wanted to go on Casey and Miwa's mission/definietly-not-date as the third wheel, but they brushed him off.
The Shredder finishes the brainworm serum and orders Leo captured for testing. The boy doesn't want to harm his former teammates, and Slash and Rockwell knock him out. Fortunately, Donnie had implanted a tracker in his brother in case the 'wild snake state' relapsed, so their parents are alerted and ready when Leo, controlled by the newer type of worm, returns to the hideout for Shen. The others free Slash and Rockwell. Donnie's paranoia literally saves the day.
Yoshi and Shen immobilize their son with pressure points, and the others, upon their return, try to force the real Leo to fight the control.
'Your leadership is way too complicated,' Raph snaps.
''Space Heroes' is boring,' Casey adds.
Leo looks like he wants to commit several crimes at once. Eventually, he spits out the worm after Captain Ryan insult.
Some things even mind control can't handle.
After Leo's release, he's rightly angry. Not just about the forced mutation or the constant threat to his life. This time, it was supposed to lead to his mother's kidnapping. What's important, Leo isn't depressed like in 'Same Difference,' but FURIOUS. After all, the Shredder's plan almost worked, but instead of dire consequences, we have 'I could have done it, I could have hurt them, and he could have made me do it,' and that drives him into pure rage.
One night, Leo alone destroys the Foot clan's laboratory, connected to another business venture. He returns in the early morning covered in soot and with a cut eyebrow. Miwa realizes it first. Raph joins in moments later.
And thus, the 'trio of destruction' is formed (something like Leonardo & Karai & Shinigami squad in the series). They even have new nicknames: Wraith, Nyx and Havoc.
Leo plans the operations. Miwa infiltrates. Raph solves everything that can't be solved quietly. Together, they secretly destroy all the Foot clan and the Kraang business for weeks, becoming nearly invincible.
Miwa 🥷: First, tactical reconnaissance.
Raph 💥: Then, brutal violence.
Leo 😎: The highest level of professional destruction.
The Kraang's laboratories and places of Foot clan's business: 🎇
Casey, 'Nyx's' biggest fan: 😍
New York also discovers that 'precision explosion' sounds much worse than it should. Warehouses, docks, factories. Seemingly random locations. They always do it at night and secretly, so the rest of the action unfolds pretty much as 'Same Difference' have it.
The remaining four and Metalhead begin investigating the mysterious vigilante group, thus forming the 'quintet of detectives.' They regularly consult their theories with the actual perpetrators.
'Why do you think they attacked that warehouse?'
Leo, who had been planning this action for three days:
'It might have been strategically important. Or maybe out of revenge, I don't know.' *
The truth only comes out later, after they literally see them returning just before dawn.
'How could we have missed that?!' Mikey groans.
Donnie slams his head on the table, and Metalhead pats him on the back.
'They were really good at camouflaging themselves. They were undetectable.'
Literally: soot, explosives in pockets, lack of sleep, and a map of the next targets under a pile of Miwa's clothes. In the background: Raph with singed hair, Leo sleeping in a sitting position, hugging his katanas, Miwa with robot shrapnel sticking out of her sleeve.
'True masters of disguise.' Casey nods solemnly.
Yoshi finally intervenes. He finds all three returning in the morning, earlier leaving despite the rest of the team's threats to report them to their parents—bruised, tired, and barely standing. Leo talks about his anger. Raph talks about wanting revenge for his brother and almost being kidnapped. Miwa talks about how the Shredder targeted her brother instead of her. She was so scared she couldn't think clearly. Now she's no longer afraid of him.
Yoshi notices the main thing:
'Family trauma is once again masquerading as ninja strategy.' The oldest three are finally letting up a bit, combining personal outings with family plans. They hadn't said anything before because their parents would have forbidden them, and they didn't want to drag the rest of the youth down with them, endangering them (despite their faith in them). Besides, a smaller group is harder to detect.
Then comes 'The Fourfold Trap' or something. Then the Triceraton plot. Then cosmic chaos.
In the final battle, Yoshi plants a bomb on the black hole generator, and the Shredder tries to kill him. And then, for the first time since the day of his mutation, Leo's hair awakens.
Black snakes with dark blue shine rise up violently and bite Saki's arm.
Leo stares at his own hair in utter shock. Honestly, he probably wasn't even aware he was venomous.
The Shredder looks even worse.
Miwa seizes the moment and plunges her tanto deep into Saki's other arm. Shen fires her crossbow, hitting him in his good eye.
This is a very bad day for Oroku Saki.
Probably his last. Not because of the venom, but because of Shen's crossbow bolt.
Moments later, Professor Honeycutt takes the youth into space to finally stop the Triceratons. I also have no idea how to continue this.
*It's not impossible at all. Just remember the scenes in episode 5 of season 1, when the boys are exhausted and injured. It's clear they sneaked out, but they're lying to Splinter, denying it so vehemently it's laughable.
In Japanese mythology, the shirohebi yokai is a white snake that can transform into a human and communicate with people as a messenger of the gods. A symbol of the kami of medicine, it is revered as a sacred guardian who protects homes from disasters, bringing followers warnings of impending good fortune or misfortune.
Before Vision Quest and during his temporary mind control, Leo's body and consciousness were incompatible, which is why he had snake-like eyes and transparent scales on his skin. He always appears this way for a few seconds after transforming into a human, which is why he wears a mask, even when he transforms in front of loved ones.
Leonardo's katanas become an integral part of his body during his mutant transformation, but as a human, he is able to distance himself from them (after a long time), although he is slightly paranoid at the time. And there is a plot with Mikey hiding Leo's katanas, an experiment to see if he finds them. Spoiler: He does. Whether the walls in his path will suffer is debatable.
Leo discovered snake arms after Vision Quest and also used them to destroy Foot and Kraang operations and in Japan. They lack katanas, so they are very flexible, able to lengthen and shorten.
I think Leo is too young for his venom to be able to kill an adult warrior like The Shredder, but it could still paralyze him.
Turtle Leo panicked slightly in the finale when he saw his human counterpart's snake form and this version of 'Karai,' because it made sense what happened in that dimension.
I like the idea that, just as Leo has a few off-white scales on a dark green background in the show (as a turtle), here in snake form he has a few light blue scales on a white background.
Spoiler for the Season 4 finale:
I like the fact that in canon, Leonardo kills the Shredder, Karai tries to, and that in the original story, Shen does it (nice symbolism). That's why Leo and Miwa paralyze/severely injure the Shredder here, and Shen finishes him off.
This entire work was inspired by SunnyLighter's story 'Same Difference' on AO3.
