Splinter is a wise and loving father, treating the turtles as his own sons but not hesitating to scold them when necessary. He does his best to look out for them and would gladly give his life to protect them. In an alternate future where the Shredder takes over the world, that is exactly what he did. This overprotective streak made him reluctant to allow them to enter the Battle Nexus competition; in fact he never even told his sons about it and they only found out because they followed him. However Splinter also shows great faith in his sons, believing them to be fully capable ninjas and even showing enough confidence in their abilities to allow them to face the deadly Shredder on multiple occasions, although during the majority of their encounters, he is there to support and protect them in any way that he can.
Splinter has a vengeful streak as shown by his determination to avenge Hamato Yoshi's murder. He speaks very highly of Yoshi, even thinking of him as a father figure despite the species differences and the fact that Splinter wasn't fully sentient until after Yoshi's death. He is one of the very few characters who challenges the Ninja Tribunal, whom he partially blames for Yoshi's death. Indeed Splinter shows blatant contempt for the Tribunal, believing them to be heartless and no better than the demon Shredder. However, after the demon Shredder is destroyed, the Tribunal explained that if Yoshi never died, he would never have existed and neither would the turtles.
Even before his mutation, Splinter showed a remarkable level of intelligence for a rat, being able to mimic Master Yoshi's movements and understand the principles of ninjitsu enough to retain and teach them to his sons. Despite Splinter's intelligence however, he has great difficulty using mechanical equipment, being unsure of how to answer a Shell Cell or control the Battleshell remotely.
Splinter is a very honorable person and is therefore disgusted by dishonor and cowardice. He is capable of fighting on par with the Shredder and also shows a great deal of cunning and resourcefulness in combat, such as when he tricked the Shredder into bringing a water tower down on himself. Despite his age, Splinter also shows amazing speed, strength and skill in combat. His simple walking stick is his signature weapon as he believes that in the hands of a true ninjitsu master, any weapon could be deadly.
In addition to his exceptional skill in physical combat, Splinter is by no means lacking in other aspects of ninjitsu. He was able to penetrate the illusion created by the Foot Mystics and he and his sons defeated them by using meditation. Splinter's keen sense of observation is assisted by his strong sense of smell. Even when his opponents are invisible, he can still pick up their scent and get at least a vague idea of where they are.
Splinter started his life as an ordinary rat in Japan who found his way into a home owned by the Ancient One. When he was discovered, his life was spared by Tang Shen, the Ancient One's adopted daughter, who took him as a pet. As in previous versions, Tang Shen became tragically caught up between Hamato Yoshi and a jealous rival, this time Yukio Mashimi, a childhood friend of Yoshi's. The two of them eventually joined the Utroms and became Guardians. But Mashimi's jealousy of Yoshi, both for his advancement as a Guardian, and the love of Tang Shen, led him to murder Shen and betray the Utroms' location to The Shredder. Yoshi killed Mashimi in revenge and went to America with the Utroms, taking Tang Shen's pet with him, and giving him the name Splinter. Later, Yoshi would be tracked down and killed by The Shredder, who tried to force him to reveal the Utroms' location. In this continuity, it was Hun that Splinter scratched as his master Yoshi was attacked, and not Shredder.
Soon after he found the turtles and were mutated by a mutagen created by the Utroms. He decides to raise them as his own and then proceeded to train them in the way of ninjutsu. When they were older, Splinter named the four turtles, from a battered book he fished out of the storm drain containing the names of Renaissance artists, which he named the Turtles after.
During the turtles infancy he gather Yoshi's remains and took the turtles to Japan to bury them near the home of the Ancient One, he informed him about Yoshi's fate, blaming the Tribunal for refusing to help. The turtles claim to have seen a Bone Demon, but was unable to see him. The next day the babies try to convince him that they see him, although he still couldn't him, he sensed his presence, so they followed the Ancient One to the Tribunal Monastery and followed the demon to the artifacts. The demon enraged by their meddling grabs the elders to kill them both. The turtles overcame their fear and broke the amulet that renders him invisible allowing the masters to defeat him. The Tribunal thanks them and senses how special the turtles are, but erases their memories of their trip, but allowed Splinter to remember, they opened a portal back to his burrow and they all went home.
Splinter repeatedly warned the turtles to never go to the surface for any reason. They disobeyed him and were secretly teaching a young boy to deal with bullies while trying to hide it. Splinter noticed how guilty they looked trying to hide their secret, but ignores it. One night he caught them topside and scolds them for teaching when they were not ready too and punished them for disobeying him.
Seasons 1-4He continued to train the Turtles in every way they could, for preparation for evil the four did not fully understand until "The Shredder Strikes Part 1" in which the TMNT learned of the Shredder's evil and hatred and how he killed Splinter's master, Yoshi. The Turtles then continued to fight the Shredder to stop the spread of evil across New York and the world.
Splinter appears most of the time alongside the Ancient One expressing his deepest concern for the safety of his sons and for the harsh teaching methods of the Ninja Tribunal when they enlisted them to fight Tengu Shredder. He has nightmares of his sons dying in battle and was grief-stricken when it appeared to come true. To his relief, his sons were merely knocked out and defeated the Tengu Shredder.
Splinter has been seen in the Fast Forward season continuously teaching his sons' and Cody Jones the ancient ways of Ninjutsu and despite how old fashioned he's shown to be in previous seasons, he too adjusted to living in the year 2105 fighting off any evil that came his way alongside his sons and Cody.
Back to the Sewer
Splinter did not make much of a physical appearance in Back to the Sewer, however he did appear as small data fragments scattered across Cyberspace thanks to Viral and the only times he was every physically shown was during the first episode of BTTS called Tempus Fugit when he was first scattered into a million data pieces and the last episode called "Wedding Bells and Bytes" when he was returned to the real world and attended April and Casey's wedding ceremony which was abruptly interrupted by the appearance of "Cyber Shredder".
Though he did appear in a few flash backs. Splinter is shown to love his sons very much.
Splinter's design was also revamped to make him look more like his design in TMNT where he now sports a Japanese goatee.
- Splinter: "We have never revealed ourselves to the other world. You have placed us all in great danger. "
- Splinter: "As you grow older, you will learn there are many ways to do the right thing. But there is no going back. I'm afraid we find ourselves at your mercy."
- Splinter: "Where there is life. There is hope."
- Splinter: "Do not lead with your shoulders Donatello."
- Splinter: "Hmm, we will call this place... "Home."
- Splinter: "Yes, but remember, one must also make time to explore the landskape within."
- Splinter "Ah, my son. So angry. Rage is a monster that will destroy you from within. Raphael, a true warrior finds balance in all things."
- Splinter: "It is dangerous for you to go about openly in the world above. You cannot simply walk amongst the humans. They will not accept who and what you are. It is as the great sage and warrior Kenji Hashimura once said, "Why walk when you can ride?"
- Splinter: "My sons, If you are to become true ninja you must work harder. Your path in life will not be an easy one. The outside world will not be a friendly place for you. You four are different in ways the surface dwellers would never understand. To survive, you must master these skills I teach you. Ninjitsu powers of stealth and secrecy. You must become kage; shadow warriors. And you must never be discovered by the outside world."
- Splinter: "Pain is a blinding force Leonardo physical and emotional.
- Splinter: "Rage is a monster that will destroy you from within Raphael."
- Splinter: "Look with your heart Michaelangelo and not your eyes."
- Splinter: "Remember, to be a true ninja you must become one with the shadows. Darkness gives the ninja power, while light reveals the ninja's presence."
- Splinter: "He serves no great purpose. He fights no great evil. He is great evil."
- Splinter: "There is nothing more restful for a ninja then regular training."
- Splinter: "Our bodies need rest to heal... And that includes your mouths."
- Splinter: "Remember my sons even the mighty oak bends before the raging storm winds.
- Splinter: "Life moves as the wheel of destiny turn night to day."
- Splinter: "A creative mind must be balanced by a disciplined body.
- Splinter: "Only be focusing on our inner strength can we overcome our enemy."
- Splinter: "Sometimes is best to sit still and answers will come."
- Splinter: "In the hands of true ninjutsu master anything can be a weapon."
- Splinter: "A weapon is only as good as the arm that wields it."
- Splinter: "How many times did a told you not to sneak out to the surface?"
- Splinter: "It is not the student place to say when a lesson is learned. The sudden place is to listen and learn."
- Splinter: "Old wounds are slow to heal."
- Splinter: "We Must learn stillness and alertness for they are the only defense against the unexpected."
- Splinter: "A ninja's greatest strength is patience."
- Splinter: "The more one learns the less one knows."
- Splinter: "Attacking a wounded soldier. You have no honor."
- Splinter: "These who become obsessed are often their worst enemy."
- Splinter: "Let your mind become pool of stillness. Break the surface explore the deeps for that is where the true wonders lies.
- Splinter: "A wise ninja does not seek out an enemy who he does not fully understand."
- Splinter: "The two greatest weapons at the ninja disposal are placement and surprise."
- Splinter: "Sometimes the past is a mirror in which we can see the reflection of what danger the future holds."
- Splinter: "Donatello, your Battle Shell is a marvel of engineering. A true testament to your incredible mechanical skills. And I never want to see it in our home again."
- Splinter: "I hate to put either one of you at risk, but only a fool ignores fate and the strange gifts it offers"
- Splinter: "Miss O'Neil, teaching them the ancient art of Ninjitsu was hard enough. I'm afraid even I cannot work miracles."
- Splinter: "You should never have tried to face The Shredder alone. He is too powerful."
- Splinter: "Master Yoshi kept his honor to the end. A true warrior, and a true Guardian."