Master Splinter

Master Splinter is the adoptive father of Leonardo, Raphael, Donatello, and Michelangelo. He raised them and taught them in the art of Ninjutsu. He is portrayed as a dark gray rat in monk's robes and is stated to weigh 90 lbs.

Personality
Splinter is a wise and loving father, treating the turtles as his own sons but does not hesitate to scold them when necessary. He does his best to look out for them and will gladly give his life to protect them. In an alternate future where the Shredder takes over the world, that is exactly what he does. 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.

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.

Splinter is a very honourable person and is therefore disgusted by dishonour 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.

Backstory
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 then proceded 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. He 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.