in the 1987 "tmnt" cartoon, splinter and yoshi are combined. he is a martial art instructor for the foot clan in japan, and also has a passion for renaissance art. yoshi is framed by his rival, oroku saki, for trying to murder their common dojo master. 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. one day, he comes across four baby turtles which were accidentally dropped by a boy through a sewer grate. splinter keeps them as pets and treats them like his children. 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. as a result, they are all affected by the leaking chemical, which is a mutagen. the mutagen combines the dna of living beings who have been in contact. thus, the turtles, being in a pet store with people touching them, turn into young humanoid turtles. yoshi, having been in contact with sewer rats, becomes a humanoid rat.