Fifteen years before Rise of the Turtles, Part 1, Hamato Yoshi and his four new pet turtles mutated, and Yoshi sought refuge underground, squatting secretly in an abandoned subway relay station, connected to a sewer and an abandoned subway tunnel. Yoshi improvised a home there, and raised the four mutant turtles as his own adopted sons and ninjutsu students, who would call Yoshi by his new name "Splinter". Sometime after their mutation, the family recovered a non-mutant tortoise who became Raph's pet turtle Spike. For 15 years, the family farmed their own algae and worms as food. Splinter's four turtle sons spent virtually all their time in the lair until their 15th mutation day, when Splinter allowed them to visit the surface for the first time in their mutant lives.