Splinter, called Takeshi Yoshihama in Japanese adaptations, is a mutant rat and the adoptive father-mentor of the Teenage Mutant Ninja Turtles. Trained in ninjutsu, he leads their battles against foes like Shredder and mutated adversaries. His Japanese name, altered from "Hamato Yoshi" to align with cultural norms, preserves his core identity while adapting to regional audiences. Originally the pet of a human martial artist, his mutation’s origins remain unexplored in the OVA, though his past as a disciplined warrior informs his teachings. He stresses teamwork, restraint, and measured power use, particularly when the turtles harness volatile artifacts like the Mutastones—alien-derived crystals granting enhanced abilities at potential cost.

Strategically guiding the turtles through clashes with transformed enemies such as Devil Shredder and Supermutant Bebop and Rocksteady, Splinter prioritizes unity and ethical combat. His mentorship, though devoid of personal backstory exploration in the OVA, consistently anchors the narrative’s focus on loyalty, balance, and the moral weight of conflict, mirroring his established role across the franchise.