In this two-part episode, the Turtles rise to the surface for the first time since being mutated, and witness the Kraang, a race of brain-like aliens with robotic bodies, capturing April O'Neil and her father, Kirby. The Turtles attempt to rescue the O'Neils while learning that the strange green ooze possessed by the Kraang could hold many secrets relating to their mutations.
The Turtles are in danger of exposure when hot-headed Raphael is caught on video arguing with a human on the street. He must learn to control his temper in order to help the others retrieve the video before it falls into the wrong hands.
To prove that Turtles can be friends with humans, Michelangelo uses a social networking site to befriend a famous martial artist who is secretly Shredder's top lieutenant.
When Donatello's latest invention gives failed inventor and perpetual loser Baxter Stockman enhanced abilities, the turtles must learn to use their heads instead of brute force to defeat him.
When Donatello loses confidence in his bo staff as an effective weapon, he constructs Metalhead, a fully armed robotic turtle based on Kraang technology.
Donatello and April investigate a scientist’s disappearance, but discover a conspiracy regarding a bizarre psychic monkey instead.
Leo fears his act of mercy has come back to haunt him when Xever holds a local noodle shop owner hostage.
After April receives a warning from her imprisoned father, she and the Turtles embark on a mission to save him and stop The Kraang from detonating a mutagen bomb in the city.
The Turtles must defend their home in the sewers when Chris Bradford tries to destroy it with a dangerous chemical.
When simultaneous threats from the Purple Dragons and Baxter Stockman’s mechanical Mousers force the Turtles to split into two groups, Donnie & Mikey must prove that their “B Team” is just as valuable as Leo & Raph’s “A Team.”
Michelangelo befriends an unstable mutant alligator, who he later names Leatherhead, possesses a strange piece of Kraang technology, but the other Turtles aren’t sure whether Leatherhead is a friend or a foe.
Tired of Raphael's constant criticism, Leonardo lets him try his hand at leadership, while Leonardo meets a female ninja, Karai, who tries to lure him to the dark side.
The Turtles must face off against a new enemy, The Rat King, who threatens not only to take control of the city, but of Splinter's mind as well.
The Turtles get their first look at high school when April's school project draws attention from the Kraang.
The Turtles meet their first fan when a teenager decides to dress up and fight crime as "The Pulverizer."
While breaking into the hostile environment of TCRI headquarters, the Turtles discover the true intent of the Kraang and resolve to stop the alien invasion once and for all.
While trying to foil a Kraang invasion plot, the Turtles are hunted by a giant cockroach.
Baxter Stockman seeks revenge on Fishface and Dogpound as well as the Turtles, and lures them all into a deadly labyrinth.
After witnessing the Kraang in action, Karai realizes the seriousness of the alien threat and proposes an alliance with the Turtles....unless the Shredder finds out.
While the Turtles are infiltrating an undersea Kraang base, the Foot Clan attempts to capture April.
Michaelangelo must fight his brothers when they fall under the control of a parasitic wasp.
When Shredder plans to create an army of mutants, the Turtles must rely on the help of the Pulverizer, who was recruited into the Foot (to be expendable) and volunteers to gather information on the inside on their behalf. When he agrees to be a test subject for a stolen supply of Kraang Mutagen, the Turtles rescue him, but not before he recklessly gets himself mutated.
Donatello breaks into a secret Kraang detention center in order to rescue Kirby O'Neil, but ends up trapped inside with a deadly prisoner called the Newtralizer.
In this two part episode, the turtles engage in a difficult battle, as they make a desperate assault on TCRI to shut down the Kraang portal.
The Turtles discover that the Kraang survived their previous showdown and have dropped mutagen canisters all over New York City.
The Turtles face an army of robot foot soldiers; Karai captures Leonardo and forces him to do battle with ninjas that can adapt to his every move.
While tracking mutagen, the Turtles bring a mutated squirrel back to the lair. When it starts multiplying, the Turtles must hunt the squirrel mutants and prevent them from escaping into the city.
Donatello experiments with mutagen in an attempt to find a cure for April's mutated father. But one of his expirements goes wrong and he is unleashed in the city.
Michelangelo plays with some mutagen, contracting a dangerous infection that mutates out of control.
April tries to resume her normal life; April realizes that she may have put her friend in jeopardy when Karai starts hunting her again.
The Turtles find themselves being hunted by a new threat -- another mutant turtle called Slash, who has a personal vendetta against the brothers.
April feels left out and insists on joining the Turtles on a mission to TCRI; A secret about April's past is revealed...
After encountering mutants and ninjas, Casey Jones decides to take on "pure evil" alone. When he meets Raphael, the two hot-headed fighters must put their dislike for each other aside and work together against a common foe.
A fungus mutant spreads through the sewers causing the Turtles to experience their worst fears. Leonardo must face his greatest fear.
After Donnie upgrades Metalhead's artificial intelligence, he must decide if he can trust a sentient Metalhead.
When the Rat King returns, Splinter must overcome his fears in order to defeat his enemy.
Leonardo considers asking Splinter for help while facing Shredder's new assassin; Donnie must put aside his rivalry with Casey in order to uncover a Kraang plot.
When the turtles play a Fantasy LARP game to get their minds off things, they separate the difference between fantasy and reality.
The Turtles create a retro-mutagen to help April's father; Baxter Stockman threatens to mutate April.
Raphael is worried about Casey's ability to handle big mutant threats especially when they meet Slash again and discover he has a partner of his own, the Newtralizer.
When Tiger Claw returns, he vows to hunt and destroy the turtles, as well as April and Casey. Meanwhile, Karai finds out the truth about her mother and real father, forcing her to make a life changing decision.
Mikey struggles to convince the others that a new mutant is trying to attack and capture people using living pizzas.
Leo tries to convince the team to rescue Karai; a master thief steals Shredder’s helmet. ("Kuro Kabuto" means "Black Helmet" in Japanese. )
Raphael accidentally damages a machine that forces him to swap minds with a Kraang. Now he must find a way to convince his brothers and Splinter that it's really him, before the Kraang controlling his body destroys his brothers or worse, reveals their location to the rest of the Kraang.
Leo stages a rescue for Karai against Splinter's wishes. While the mission is a success, Karai's knowledge of the truth makes her rush out to take her revenge on Shredder for killing her mother and lying to her for so long, leading to an unexpected turn of events.
Donnie becomes increasingly jealous of April and Casey's relationship; April is kidnapped by an evil spirit who intends to drain her powers.
When the Turtles go to the bizarre realm of Dimension X, Mikey is the only one who can figure the place out.
Leo and Donnie disagree about their plan to stop the Kraang invasion; Donnie must step up as the leader of the bunch when Leo makes a mistake and is separated from the team.
Narrowly escaping from the Shredder and the Kraang, the turtles, April, and Casey take shelter at April's family farmhouse upstate to recover and figure out how to stop the Kraang. The turtles deal with not having Splinter around and the possibility of Leo not making a full recovery, and a mysterious creature stalks the group.
When the Turtles discover Bigfoot in the woods, Donnie befriends it and insists they protect it from a hunter.
When the guys discover a Kraang ship buried under April's house, they also uncover April's lost mother.
After getting in trouble for trashing the house, Michelangelo gets upset and flees. After meeting the Napoleon Bonafrog, a member of the Punk Frogs, he unknowingly joins them in a plan to capture the humans and take over the city.
When the Turtles are trapped in their dreams by creatures, April and Casey must figure out how to wake them up.
When Casey and Donatello bond while building Casey's new hot rod, the bond is challenged by a hot-rodding mutant.
When Casey, Raph, Mikey and Donnie are captured by a new mutant, April and Leo must overcome disabilities in order to save them.
Leo takes the Turtles to train in the woods in an advanced ninja ritual; the Turtles must overcome their weaknesses and face their enemies to become a true ninja.
When the Turtles return to the city to search for Splinter, they discover that the city has been overrun with Kraang.
As the Turtles search for Karai, they are forced to deal with a city filled with Kraangdroids as well as Zeck and Steranko.
Donnie finishes a new batch of retro-mutagen in hopes of saving Karai; the Turtles are hunted by Shredder's new henchmen, Bebop and Rocksteady.
While the Mighty Mutanimals lay siege to TCRI, the Turtles must brave the bizarre world of Dimension X to save the enslaved people of New York.
Annoyed he was left out of the fight against the Kraang, Casey hunts down the Purple Dragons and Shredder to prove he just as great as the turtles.
A new and unfamiliar mutant known as Muckman begins to gain notoriety as New York City's 'Monster Hero.'
The Shredder kidnaps and experiments on the Mighty Mutanimals.
A skateboarding reptilian becomes friends with Mikey and Casey.
Karai becomes brainwashed and goes after the turtles.
The turtles travel through time because of an apprentice's actions, and they must unite to combat Time Master Savanti Romero.
When the Turtles are accidentally transported to the past, they happen to cross paths with a familiar ninja clan.
Leonardo decides to sneak into Shredder's lair alone, and winds up facing the biggest mutant threat yet.
After an accident, Donnie finds himself slowly losing his intelligence.
The Turtles are baited by an unknown enemy into deadly traps.
Raph makes a new friend named Zog, an alien Triceraton.
When the turtles get word of the Kraang's return, they realize there is an even bigger threat coming to Earth.
The fugitoid brings the gang to 6 months in the past in order to prevent the Triceratons getting the parts of the black hole generator that was used to destroy the Earth. However, after stopping to get fuel, they end up causing lots of trouble at the port.
The Turtles and their enemy crash-land on an ice moon and they must put aside their differences in order to survive.
Casey releases a wish-granting alien named Wyrm, who wants his freedom to do whatever he wants to the universe.
A shark-like bounty hunter is hired by Lord Dregg to destroy the turtles, who choose to hide out in an abandoned space station.
When microscopic aliens invade Mikey's mind, the Turtles have to chase them through the strange world of Mikey's subconscious.
The Turtles find themselves on a planet of pure evil.
The Turtles are captured by the Triceratons and are forced to fight in a gladiator-like arena for their lives.
The Turtles must gain the trust of the Utrom Council in order to find the next piece of the black hole generator.
The Turtles journey through an ocean-like area of space.
The Turtles are transported to another dimension where they meet their 1980s counterparts and work together to battle Krang.
Donatello is feeling inferior to Fugitoid, but his intellect is put to the test when the Triceratons attack.
When Raphael loses his fighting mojo, he must overcome his feelings to save his brothers from certain doom.
The team must overcome impossible odds in order to obtain the final Black Hole Generator piece that is located on the planet Magdomar.
As the team finally reaches Earth, Fugitoid reveals a horrible secret about his past.
April faces a deadly new enemy when she graduates to full Kunoichi; the Turtles must deal with the return of some old foes.
When Leonardo secretly allies himself with Karai, he gets himself into deeper danger than he could have realized.
Raphael must overcome his fear of insects to lead the team when they are forced to battle Stockman-Fly's new insect minions.
Don Vizioso's gang tracks the Turtles with a slew of Anti-Mutant weapons.
Donnie experiments with April's fragment of the mystical Sol Star (which she is becoming quite obsessed with, due to its mighty power drastically strengthening and further developing her psionic abilities), but accidentally supercharges it with electricity, that stirs sudden sentience and autonomy in the crystal fragment. It then uses this to bring four of the main characters from Mikey's favorite comic book to life. Mikey easily befriends the heroes Wingnut and Screwloose, and he and Casey join them in stopping crime. But when they tell the two superheroes about the fact that they're fictional characters, and show them the Soul Star, it causes Wingnut and Screwloose to transform into insane monstrous forms. Meanwhile, Donatello becomes incessantly worried that the Sol Star fragment is affecting April's mental stability.
For the first time, the Turtles encounter something they cannot defeat – the Super Shredder!
The Turtle team hunts for their Sensei, but soon realizes they are being hunted as well.
Donatello becomes concerned and decides to test April, only to discover that her psychic abilities are rapidly growing in power.
Raphael's bonding with little Chompy gets interrupted by the invasion of Tokka, who has come to Earth searching for him.
A dangerous female mutant by the name of Alopex appears with a personal vendetta against Tiger Claw.
Splinter must lead the turtles and the Mighty Mutanimals on the hunt to defeat his old enemy.
With the demise of their beloved father and Karai incapacitated, the Turtles, April, and Casey infiltrate Super Shredder's new lair to put an end to Oroku Saki once and for all, no matter what it takes.
The Turtles believe they have defeated most of their old enemies, but they soon discover that a new evil is rising from the ashes.
Karai searches for the legendary Kuro Kabuto, claiming to be the rightful heiress of the Foot Clan, when she suddenly encounters an old rival.
Donnie's grudge with Don Vizioso threatens the Turtle's newest mission.
The Turtles must defeat the mighty demodragon Kavaxas to prevent him from destroying the world.
When Splinter first mutates, he must learn to survive the life of a mutant on the run while also protecting four baby mutant turtles.
When Renet (Mikey's crush from the future) returns, the Turtles must help her stop Savanti Romero from unleashing an undead army on modern-day New York by traveling back in time.
Count Dracula is awakened, and turns Raphael into a vampire.
Savanti recruits Frankenstein's Monster and will soon unleash his creatures on the 21st Century.
When Renet and the Turtles return to a world run by monsters, they realize they have made the situation even worse.
When Mona Lisa suddenly arrives on Earth, Raphael must get her and Bishop to work together to defeat an alien threat and save the Earth.
The 1987 Shredder and Krang recruit the 2012 Bebop and Rocksteady, finding them better than their own incompetent counterparts.
The Turtles are transported to an alternate dimension where they meet the rabbit samurai, Miyamoto Usagi.
Usagi leads the Turtles through a haunted forest where they encounter mischievous and dangerous spirits.
As they reach their destination, Usagi and the Turtles must help Kintaro fulfill his destiny.
In an alternate, apocalyptic future that takes place fifty years later, all humans and most of the mutant population have been wiped out, due to an extremely powerful mutant explosion that had mysteriously occurred through unknown means. Only a weathered Raphael, who has most of his childhood memories lost to him, and Donatello (whose consciousness has been transferred into Metalhead) have been traveling throughout the Impossible Wasteland trying to save alive while being pursued by the Verminator and his bikers. Befriending a female meerkat warrior named Mira, the last of her tribe, who harbors the secret to "Paradise" and that she must find a wise turtle called "the Holy Chalupa."
