[1] The third season tells the story of the Turtles, April O'Neil and Casey Jones, who are required to abandon their lair in the New York City sewers to Northampton, Massachusetts, to their eventual return home and driving out the Kraang and undo their hold on the hundreds of mutated humans.
[2] Seth Green assumed the role beginning in season 3; in the show's universe, the change of voice was explained due to Leonardo having wounded his vocal cords.
The Turtles also deal with not having Splinter around, the possibility of Leo not making a full recovery, and a mysterious creature that is stalking the group.
After meeting a member of the Punk Frogs named Napoleon Bonafrog, he unknowingly joins them in a plan to capture the humans and take over the nearby city.
Now trapped sixteen years in Tokyo, Japan's not-too-distant past, after an accident with Renet's Time Scepter, the Turtles encounter a sixteen-year younger Hamato Yoshi and Oroku Saki, in the middle of their escalated rivalry over Tang Shen's heart, and the infant Miwa's stolen life and future as Karai.