Mutant turtles Leonardo, Donatello, Raphael and Michelangelo are trained in the art of ninjutsu. The four learn to rely on each other as they unravel the mystery of their existence and train to become the heroes they are destined to be.
When Shredder teams with the Kraang to receive a batch of mutagen, the Turtles' problems only get worse - putting their friendship with April at stake. (S2, ep1)
The Turtles bring a mutated squirrel back to the lair. When it starts multiplying, the Turtles must prevent the mutants escaping into the city. (S2, ep3)
When the Turtles face Shredder's new army of robots, Karai captures Leonardo and forces him to battle these ninjas that can adapt to his every move. (S2, ep2)
Donatello experiments with mutagen in a bid to find a cure for April's father. Unfortunately this puts April in danger from a new threat - Mutagen Man! (S2, ep4)
Michelangelo is tired of being the "runt of the litter." But when he fools with some mutagen, he gets a dangerous infection that is mutating out of control. (S2, ep5)
Target - April O'Neil: April tries to resume a normal life, but when Karai starts hunting her again, April realizes she may have put her new friend Casey Jones in danger as well. (S2, ep6)
The Turtles find themselves being hunted by a new threat - another mutant turtle called Slash, who has a personal vendetta against the brothers. (S2, ep7)
The Good, The Bad, and Casey Jones: After mutants and ninjas, Casey Jones decides to take on "pure evil" alone. When he meets Raphael, the two must unite against a common foe. (S2, ep9)
Feeling left out of the action, April insists on joining the Turtles on a mission to TCRI, where they learn a shocking secret about April's past. (S2, ep8)
A fungus spreading through the sewers causes the Turtles and April to experience their worst fears as Leonardo must face his greatest fear - losing his team. (S2, ep10)
When Donnie upgrades Metalhead's artificial intelligence, he must decide if he can trust a sentient Metalhead... or if he has created a new foe. (S2, ep11)
When the Rat King returns, Splinter must overcome his guilt and fear of the Rat King controlling his mind in order to defeat his foe once and for all. (S2, ep12)
The Manhattan Project - Part 1: Leo must decide whether to risk his team's lives or ask for Splinter's help. Donnie must put aside his rivalry with Casey Jones to uncover a new Kraang plot. (S2, ep13)
The Manhattan Project - Part 2: Leo must decide whether to risk his team's lives or ask for Splinter's help. Donnie must put aside his rivalry with Casey Jones to uncover a new Kraang plot. (S2, ep14)
The Turtles try to relax by playing a fantasy role-playing game, but when the game becomes real, they must learn the difference between fantasy and reality. (S2, ep15)
The Lonely Mutation of Baxter Stockman: Feeling guilty about April's father, the Turtles plan a way to help him. But then Baxter Stockman threatens to mutate April. (S2, ep 16)
Raph is worried about Casey's ability to handle big mutant threats, when they meet Slash again and discover he has a partner of his own - The Newtralizer! (S2, ep 17)
Mikey discovers that a new mutant is trying to attack and capture people using living pizzas, but he struggles to convince the others who don't believe him. (S2, ep 19)
Tiger Claw returns and intends to destroy the Turtles at any cost. (S2, ep 18)
Leo tries to convince the others to rescue Karai. Meanwhile, a thief steals Shredder's helmet and it falls into the Turtles' unsuspecting hands. (S2, ep 20)
Raph's hot-headed impulsiveness lands him in deep trouble when he accidentally damages a machine that forces him to switch minds with a Kraang. (S2, ep 21)
Leo goes behind Splinter's back when he stages a rescue for Karai, whose desire for revenge against Shredder brings about grave consequences for them all. (S2, ep 22)
As Donnie becomes increasingly jealous of April and Casey's relationship, April is kidnapped by an evil spirit who intends to drain April's powers. (S2, ep 23)
Leo and Donnie disagree about their plan to stop the Kraang invasion. When Leo makes a critical mistake, Donnie must step up as a leader. (S2, ep 25)
Leo and Donnie disagree about the plan, but when Leo makes a critical mistake, he is separated from the team, and Donnie must step up as a leader. (S2, ep 26)