[1][2] A mutant rat, he is the grave and stoic sage of the Turtles, their ninjutsu and martial arts instructor, and their adoptive father.

In both the original comics and the live-action movies, Splinter is a pet of a ninja named Hamato Yoshi in Japan, and uniquely intelligent for his species.

Splinter names the four turtles Leonardo, Donatello, Raphael, and Michelangelo (after a book on Renaissance artists that he found in a storm drain) and trains them in the arts of ninjutsu so that they can avenge his dead master while raising them as his own sons, as well as educating them.

After a bad encounter with humans, Splinter decided to learn ninjutsu from online videos and Jackie Chan movies and teach it to his sons.

Unable to prove his innocence and expelled from the Foot Clan, Splinter moves to New York City, where he lives as a hermit in its sewers and befriends the rats.

When he finds the turtles near some broken barrels that are oozing glowing pink, later retconned to green, chemical liquid, he tries to clean them with his bare hands.

Yoshi raises the turtles by himself and gives them the names of his favorite Renaissance artists: Leonardo, Donatello, Raphael, and Michelangelo.

Yoshi is given the nickname "Splinter", due to his proficiency at breaking wooden boards, and he teaches them the art of ninjutsu in order to protect themselves.

Despite not having that father/son relationship with the turtles, Splinter, in the episode "The Old Switcheroo", shows a glimpse of fatherly concern for Leonardo when he is injured by one of Donatello's contraptions.

[3] The 1990 live action concert tour entitled "Coming Out of Their Shells", saw Splinter described as the rat owned by Hamato Yoshi mutated to a humanoid form, rather than Yoshi himself mutated into a ratlike body, bringing him more in line with the original Mirage Comics incarnation as well as that of the then recently released feature film, which also followed the Mirage origin.

In the concert events, he is still the Turtles' mentor in the martial arts, as well as encouraging their musical pursuits, and sings the track Skipping Stones as a solo ballad.

Peter Reneday reprises his role as the voice of Splinter with the exception of the song Skipping Stones, though both the show's Pay per view and VHS cast lists both leave him uncredited.

After moving to New York City, Yoshi has just purchased four pet turtles when he stumbles upon an exchange in an alley between two Kraang droids.

As the result of stepping on the tail of a black rat upon entering an alley, Yoshi mutates while the Turtles take on human characteristics.

Realizing he can no longer live a normal life, he retreats to the New York sewers where he raises his pets as sons and teaches them ninjutsu.

Reluctantly allowing the group to get involved, Splinter appoints Leonardo as their leader and continues to offer counsel and lessons as they engage various foes.

He is eventually able to convince Karai of the truth about their past, but she subsequently mutates into a snake-like being when Shredder's plan for revenge backfires.

The turtles hold him one last time before they, Casey and April flee with Fugitoid, as he arrives at the very last moment in a spaceship as Earth is sucked into a black hole.

After the crisis is stopped, Splinter has a final goodbye with his family and friends, and his spirit peacefully floats into the sky and returns to the afterlife once more.

When Yoshi openly objects to the needless slaughter of a village connected to an assassination target, he and his family are declared traitors.

In Rise of the Teenage Mutant Ninja Turtles, voiced by Eric Bauza and Sander Argabrite (as a younger version of the character), Splinter is once again Hamato Yoshi, a descendant of the Hamato clan; however he is presented as ex-martial arts film star "Lou Jitsu" (taking inspiration from Jackie Chan and Bruce Lee) with an extremely relaxed attitude to life.

He lives with his sons in their sewer lair and can be seen spending his time reliving his glory days by rewatching his movies as an action hero before he had been unexpectedly mutated into a rat.

Yoshi escaped his responsibility as a Hamato due to his mother being forced to leave him, nursing a growing resentment towards his clan until his departure.

Afraid that his sons would be put in harm's way he is less diligent in training them in ninjutsu, until he learns that the Foot Clan have been assembling the Shredder's armour, and he takes a more active role in preparing them for the danger his irresponsibility has placed them in.

Splinter shows a great aptitude in using anything as a potential weapon, as shown in his films' he fights with Fish and Ladders in the episode 'Evil League of Mutants'.

Splinter's physical appearance remains fairly consistent in all incarnations of the character; he is portrayed as an elderly rat dressed in robes.

Splinter cares for his adopted sons with fierce devotion, rescuing them in very critical moments in the series, such as when Shredder attempted to execute the four on a building, or when Bishop tried to literally tear them apart for science.

In the 2018 series, Splinter is displayed as somewhat irresponsible given his different history, spending most of his time eating and watching TV, although he occasionally shows the traits mentioned above.

Splinter appears as a supporting character in most video games based on the Teenage Mutant Ninja Turtles franchise.

In Teenage Mutant Ninja Turtles on the Nintendo Entertainment System, he transforms back into a human if the player reaches the ending.