Master Splinter is the Ninja Turtles’ teacher, father, and moral center. Almost every major TMNT version includes him, but they do not all tell the same story about how he became a mutant rat.
The four brothers usually begin as ordinary turtles exposed to mutagen. Splinter’s past is much less consistent.
One broad version starts with an actual rat, often the pet of martial artist Hamato Yoshi, who eventually mutates and raises the Turtles.
The other begins with Yoshi himself, a human martial artist transformed into a rat by mutagen.
Some continuities follow one route closely. Others combine the two or invent a different connection between Splinter, Yoshi, and the family he builds.
Let’s begin with the versions in which Splinter starts life as a rat.
The Original Mirage Comics
In the first Teenage Mutant Ninja Turtles comic, Splinter is Hamato Yoshi’s pet rat. Watching from his cage, he imitates his owner’s ninjutsu practice and gradually learns the movements.
Yoshi belongs to the Foot Clan. Another member, Oroku Nagi, is his rival, particularly over Tang Shen, who loves Yoshi rather than Nagi.
Nagi attacks Shen after she rejects him. Yoshi arrives, sees the assault, and kills Nagi in a rage.
Killing another member of the clan places Yoshi in a desperate position. Rather than die to restore his honor, he flees to New York with Shen and Splinter. There he tries to start again by teaching martial arts.
Back in Japan, Nagi’s younger brother, Oroku Saki, grows up consumed by revenge. He trains until he becomes one of the Foot’s most formidable warriors. Sent to lead the clan’s American operation at eighteen, he sees his chance to find Yoshi.
Saki turns the New York Foot into a criminal organization and becomes the Shredder. He murders Shen, then kills Yoshi when he returns home and confronts him.
Splinter escapes and survives on the streets. He later witnesses a traffic accident involving a truck, a young man saving a blind pedestrian, a canister, and a child carrying four turtles. The broken container’s contents spill onto the turtles as they fall into a storm drain.
Splinter follows, gathers them up, and takes them to his shelter. All five begin to grow and change. He raises the brothers as sons, teaches them ninjutsu, and names them after Renaissance artists from an old book. His original mission for them is also personal: avenge Yoshi and Shen by confronting their killer.
Teenage Mutant Ninja Turtles (1990)
The first live-action movie keeps the essential pet-rat origin. Splinter learns by copying Hamato Yoshi’s movements from inside his cage. When April first visits the sewer lair, he tells her part of the story of his family.
A later account explains his physical connection to Shredder. During Yoshi’s murder, Splinter leaps at Oroku Saki and scratches his face. Saki strikes back, cutting Splinter’s ear. The movie simplifies the original comic’s wider rivalry rather than reproducing every detail.
Near the end, Splinter faces Shredder on a rooftop. He avoids the villain’s attack and leaves him falling into a garbage truck below. Casey Jones then activates the compactor. Shredder’s apparent defeat closes the first film, though the sequel reveals that he survived.
Teenage Mutant Ninja Turtles (2003)
The 2003 cartoon draws heavily from Mirage, including Splinter’s life as Yoshi’s rat. It changes the human relationships and the reasons Shredder pursues Yoshi.
As children, Hamato Yoshi and his friend Yukio Mashimi live on the streets. The Ancient One recognizes their potential, takes them in, and teaches them ninjutsu. They grow up alongside his adopted daughter, Tang Shen.
When Mashimi tries to kill a rat that enters the house, Shen stops him and keeps it as a pet. Both young men fall in love with her, but she chooses Yoshi. Mashimi’s jealousy slowly poisons their shared life.
Yoshi and Mashimi later intervene when Foot ninjas attack a man. The stranger is Mortu, a Utrom using a robotic body. Impressed by their abilities, he recruits them into the Guardians, the human allies protecting his people from Shredder.
Yoshi advances while Mashimi feels increasingly left behind. His resentment leads him to murder Shen and betray the Guardians, revealing the Utroms’ location to the Foot.
Yoshi confronts and kills Mashimi, then escapes the Foot’s base. He eventually moves to New York with Shen’s pet rat. The name Splinter evokes the Ancient One’s warning that revenge can remain under the skin and keep causing pain.
Shredder tracks Yoshi down and tortures him for the Utroms’ location. Splinter tries to intervene when Hun attacks, but cannot save his owner. Shredder kills Yoshi, leaving the rat alone.
Splinter later witnesses the accident involving mutagen and four young turtles. Their transformation and the family he forms follow the familiar outline of the original comics.
Ninja Turtles: The Next Mutation
The live-action series keeps Splinter in the familiar role of a mutated rat and patient martial-arts teacher. He usually has a piece of advice ready, even when the younger heroes are difficult to manage.
He meditates in the supernatural Dream Realm and enjoys chess with his blind friend Andre.
His calm manner does not make him harmless. He can still take on groups of enemies when the family needs him.
The show ended after one season, so it never provided a complete long-term resolution for Splinter’s struggle with enemies such as Dragon Lord. Ideas associated with an unmade second season should not be confused with events shown in the series.
The Michael Bay-Produced Movies
The 2014 film begins with Splinter and the turtles as laboratory animals involved in Dr. O’Neil’s research. As a child, April visits her father’s lab, cares for the animals, feeds them, and gives the turtles their names.
When a fire destroys the laboratory, April saves the animals and releases them into the sewers. Splinter remembers her kindness, connecting their new lives to a human who once protected them.
As their experimental treatment changes their bodies and intelligence, he adopts the turtles as his sons. Fearing how humans will react, he keeps them underground. An old ninjutsu book becomes the basis for teaching himself and the boys to defend their family.
At the end of Out of the Shadows, he watches proudly as his sons receive the keys to the city. For a father so concerned about rejection, the gesture offers a measure of acceptance.
Teenage Mutant Ninja Turtles: Mutant Mayhem
This Splinter begins as a lonely rat treated badly by humans and rejected by other animals. His brief friendship with a cockroach named Kevin does not end happily either.
He finds four small turtles near a strange green liquid in the sewers. Their friendliness wins him over, and he takes them in. Contact with the substance transforms all five into larger, more intelligent beings.
They gradually become a family: Splinter is their father, and the four turtles are his sons.
An attempt to venture into the human world ends in fear and hostility. Splinter becomes determined to protect his children from being hurt in the same way.
The family learns martial arts from movies, videos, and online tutorials, turning screen time into an improvised ninja education.
Despite his age and anxious parenting, Splinter remains a remarkably fast and capable fighter.
The film also gives him an unusual romantic connection with Scumbug. For a rat whose first friend was a cockroach, finding affection with an insect mutant is a fitting turn.
The IDW Comics
IDW combines the human and animal origins through reincarnation. Splinter is both a rat transformed by mutagen and the reborn Hamato Yoshi.
In feudal Japan, Yoshi is a Foot ninja married to Tang Shen, with four human sons.
His commitment to his family creates friction with Oroku Saki, who regards it as a challenge to his obligations to the clan.
After violence against the family leaves Shen dying, Yoshi confronts Saki, now the Foot’s leader. The conflict condemns him and his children as enemies.
Yoshi escapes into the mountains with the boys, raises them alone, and teaches them ninjutsu. Saki eventually finds them and has the family executed.
Centuries later, they are reborn as animals used in StockGen experiments: Yoshi as Splinter, and his sons as the four turtles. Experimental treatment sharpens the rat’s intelligence and helps him remember his human life. Mutation gives them humanoid forms, but Splinter continues to identify with the father he once was.
This is one of the morally hardest versions of the character. He manipulates allies, tests his sons through deception, kills enemies, and eventually leads the Foot after defeating Shredder. His increasingly ruthless decisions strain his relationship with the boys.
Now let’s turn to the versions in which Splinter begins directly as a human and mutates into a rat.
Teenage Mutant Ninja Turtles (1987)
The classic cartoon gives Hamato Yoshi a new origin that, to me, makes his martial-arts knowledge easier to understand. Oroku Saki frames him during a visit from a respected master, pinning his clothing so he cannot bow. Expelled from the Foot, Yoshi flees to New York and ends up living in the sewers, surrounded by rats.
Four pet turtles fall through a drain and come into his care. When strange ooze reaches them, Yoshi touches it as well. In this cartoon’s mutation rules, his recent contact with rats turns him into one, while the turtles take on humanoid traits. He names them after Renaissance artists and teaches them ninjutsu, knowing they will need protection in a world likely to fear them. Meeting April O’Neil draws the family into Shredder’s plans for New York.
The Archie Comics
Teenage Mutant Ninja Turtles Adventures begins by adapting the 1987 show, keeping Splinter’s original identity as the human Hamato Yoshi.
As the comic moves into original stories, he takes a more active role in the team’s adventures.
This continuity also gives April O’Neil early ninjutsu training under Splinter, expanding her role beyond that of the friend who needs rescuing.
Teenage Mutant Ninja Turtles (2012)
Here, Yoshi and his adopted brother Oroku Saki grow up in the Hamato family. Yoshi marries Tang Shen, and they have a daughter, Miwa. Saki also loves Shen and resents the family she chooses with Yoshi.
His anger deepens when he learns that he was born into the defeated Foot Clan and adopted by the Hamatos. What they regarded as raising a child, he comes to see through the lens of his original clan’s destruction.
Saki attacks Yoshi at home. During their fight, Shen is fatally struck and the house burns. Saki escapes with Miwa and raises her under the name Karai.
Believing he has lost his family, Yoshi moves to New York. After buying four turtles, he notices the Kraang making a suspicious exchange. A confrontation breaks a mutagen container, exposing him and the animals. His contact with a rat determines his new form. Realizing that humans will fear them, he takes his adopted sons into the sewers.
This Splinter is an exceptionally formidable fighter, but his enemies can reach him in other ways. The Rat King exploits his mutated nature to control him, while Shredder’s obsession eventually leads to one of the series’ most devastating deaths.
Rise of the Teenage Mutant Ninja Turtles
Hamato Yoshi descends from the clan that defeated Shredder centuries earlier. His family trains to prevent the villain’s return.
As a child, he hears the clan’s history from his grandfather, Hamato Sho. His mother, Hamato Atsuko, leaves to fulfill her duty to the family’s mystical tradition, a loss that devastates him.
Years of training do not erase his resentment. He begins to reject the clan’s demands and doubt the threat that has governed so much of his life.
After an argument with his grandfather, the teenage Yoshi leaves to pursue a very different dream: becoming a movie star.
His martial-arts skill makes him famous as Lou Jitsu, first in Japan and then in the United States.
His grandfather later visits and asks him to abandon the film career and return to his family responsibilities.
Yoshi refuses. The break leaves him with regrets that the fame cannot entirely hide.
During his movie career, he meets Big Mama and falls in love. He does not initially understand her supernatural identity or the business she operates.
When he tries to propose, she abducts him and takes him to the Hidden City. Forced to fight in the Battle Nexus, he becomes its greatest champion over years of captivity.
Eventually, he refuses to keep fighting. Big Mama responds by imprisoning him.
His reputation attracts Baron Draxum, who wants Lou Jitsu’s DNA for a mutant army. Yoshi allows Draxum’s servants to take him away because it offers a possible escape from the arena.
At the laboratory, he realizes that Draxum plans to use innocent turtles in the experiments. He tries to intervene.
Draxum’s mutagen combines the turtles with Yoshi’s DNA, giving the four brothers a direct biological connection to the martial artist.
Yoshi refuses to leave the animals to become someone else’s soldiers. He takes them and fights his way out.
A rat bites him during the escape, and exposure to mutagen transforms him as well.
He leaves the Hidden City and raises the four brothers in New York’s sewers. Calling them after Renaissance artists gives the family another link to the familiar TMNT tradition, even though this father has a remarkably different past.
Splinter has appeared in many more TMNT stories, but these major comic, movie, and television versions show why a simple question—“Was he a rat or a human?”—can have so many answers.