During its premiere weekend the series reached nearly 12 million total viewers. On July 10, , at San Diego Comic Con International, Nickelodeon announced a episode pick-up for season five, as well as confirming that season four would also consist of 20 episodes.
Michelangelo 's new catchphrase is " Booyakasha " which Greg Cipes himself-plays Michelangelo- came up with instead of " Cowabunga "  and his brother, Raphael , also has an un-mutated pet turtle named Spike.
The series follows the four Ninja Turtles living in the underground sewers of Manhattan , where they're being trained in martial arts by the ratlike Master Splinter.
Two video game adaptations were released in for the show, the abysmally reviewed Teenage Mutant Ninja Turtles: Out of the Shadows with the Turtles' radically redesigned from their television likenesses , followed shortly by kid-friendly Teenage Mutant Ninja Turtles this one with the series aesthetics , which was slightly better received. In a unique touch, each season of the show features the Turtles watching a cheesy animated show Space Heroes that usually foreshadows events of an episode which was outright lamp shaded on one occasion.
Before even finishing its first season, the series was renewed for a second and third season on October 2, and February 26, respectively. The first season concluded on August 8, with 26 episodes. Season 2 debuted on October 12, and concluded on September 26, with another 26 episodes. Season 3 was released on October 3, one week after the Season 2 finale and concluded on September 27, Season 4 aired on October 25, and concluded on February 26, , both seasons contained 26 episodes per season.
The fourth season is the only season that has aired over a year, whereas the other seasons air less than a year. After a five year run spanning five seasons and episodes, the show concluded on November 12,      and will be succeeded by a new 2D animated reboot series which was revealed under the title Rise of the Teenage Mutant Ninja Turtles , set to replace this series on Nickelodeon in September of It's the turtles' fifteenth birthday and they're itching to venture up to the surface and showcase their ninja skills.
Master Splinter reluctantly agrees. At first, they love the surface with its weird lights and even stranger food like pizza. However, things go awry when they witness a girl and her father being abducted by men in a van. They try to intervene, but don't fare well during the fight, with the van getting away, only to discover that the kidnappers are really robots with living brain creatures in their chest and were carrying the ooze that made them into mutants.
Eager to learn more about this strange connection, they regroup and begin to practice fighting as a team with Master Splinter appointing Leonardo as The Leader. After storming the enemy fortress, they learn that these creatures are called "The Kraang" and have sinister plans in store. They manage to rescue the girl, April, but the Kraang still have her father.
They vow not to rest until they rescue him. Unfortunately, the Turtles' attack has not gone unnoticed by the media, which alerts The Shredder to come to New York to take on Hamato Yoshi's students himself.
What ensues is the escalating war between the Foot and Hamato Clan, a Myth Arc that turns out to have been in the works for far longer than most of the cast knows, as well as the unraveling mystery of the Kraang's agenda for Earth and humankind.
Plot Season 1 Ninjutsu master Hamato Yoshi Splinter is carrying his four pet turtles through the streets of Manhattan , New York City when he encounters members of an alien race called the Kraang. During an altercation with these aliens, Yoshi and the turtles are exposed to a mysterious radioactive alien chemical substance ooze called Mutagen which causes organic beings to undergo major physical transformations.
Yoshi becomes and takes of the characteristics of a humanoid brown rat and the turtles become anthropomorphic, they take on human characteristics. Taking upon the new name "Splinter", he retreats to the New York City sewers via the subway tunnels, where he finds an underground chamber, raises the four turtles as his adopted sons and imparts to them his knowledge of ninjutsu. Now teenagers, the Turtles Leonardo , Raphael , Donatello and Michelangelo venture to the surface for the first time in 15 years and learn that the Kraang are using the mutagen as part of their plan to take over all of New York City.
Donatello develops a crush on April. While Kirby remains a prisoner of the Kraang, April becomes an ally of the Turtles, who try to help her locate her father.
April is also trained by Splinter to be a kunoichi or female ninja. The Turtles also learn that Splinter's long-time archenemy Oroku Saki Shredder has come to New York City and has ordered his Foot Clan to track down Splinter and his sons, and put an end to their clan.
This family feud eventually earns the coincidence of two of Shredder's disciples, martial arts star Chris Bradford and Brazilian street thug Xever Montes, getting mutated into Dogpound later Rahzar and Fishface. Furthermore, Shredder recruits former TCRI inventor and mad scientist Baxter Stockman after his mousers cross paths with Dogpound threatening some Purple Dragons to hack into April's phone the Turtles are successful in rescuing April's phone The Turtles also encounter and defeat Dr.
Victor Falco, also known as 'The Rat King', who, along with having an army of New York rats, tried to brainwash Splinter into joining the dark side. Learning about the Kraang's presence through his adopted daughter Karai , Shredder enters an alliance with the aliens to destroy their mutual enemies in the Hamato Clan. At one point, Karai considers offering an alliance with the Turtles to annihilate the Kraang once she sees the seriousness of an alien threat and informs them that Shredder blatantly disregards their presence, in addition to offering them secret access to a shipment of weapons especially a rocket launcher at the dockyard to take down the UFO, but this comes after she peskily stalks and duels with the Turtles mostly Leonardo, who realizes that he may have feelings for her , and tracking them down to a facility where a major battle ensues before treacherously and selfishly abandoning them to fight a mutant she slyly, heedlessly and intentionally created furthermore, Karai was so untrustworthy, that she was agreeing with Raphael that she poses a menacing threat.
Because of her recent betrayal and her deceitful nature , the Turtles are initially skeptical, but later come to an agreement with her. However, when they sneakily ambush Shredder at the docks, it costs the Turtles especially Leonardo her friendship, when they learn that she considers Shredder as his 'father'. Afterwards, Shredder interrogates a captured Kraang droid, who speaks sufficient English to inform him that the Turtles are sheltering April, who is key to the alien's plot.
Eventually Turtles are successful with thwarting this Kraang plot. Meanwhile, April narrowly eludes Karai after a lengthy chase and after the two girls duke it out in an alley. Upon returning to Splinter and the Turtles, she decides to take shelter at the Turtles' underground sewer lair for an extended time to train with Master Splinter while the Turtles face double the threat, as Shredder begins to ally himself with the Kraang.
The Turtles discover that the Kraang led by Kraang Prime with Kraang Sub-prime as his second-in-command are a corrupted extraterrestrial race of Ultroms from outer space. The Kraang needed April's unique mental energy, and they tried to use it to perfect the planetary mutation mechanism to the Turtle's reality as it was mentioned earlier that the mutagen didn't work like the Kraang thought it would on Earth.
After the Turtles rescue Kirby, the Kraang invade New York , but the Turtles and April emerge triumphant when they are able to send the Technodrome crashing into the sea the Atlantic Ocean.
Leonardo makes a heroic sacrifice, trying his best to hold off Kraang Prime and is seemingly killed, but also emerges alive and ultimately unharmed, having narrowly escaped at the last second. Meanwhile, Splinter battles Shredder and learns that Karai is technically his Yoshi's own long-lost birth daughter, Miwa who was kidnapped by Shredder and who believes that Splinter killed her mother. Unable to fight her, he retreats in sorrow.
The first season ends with Turtles and April celebrating their victory over Kraang as Splinter hides this secret of Karai's true identity of Miwa from them, but promises to divulge this information for another day.
Meanwhile, on the sea bed, the crashed Technodrome relights, indicating that the fight isn't over yet Season 2 Some time after their victory in the Season 2 premiere, the Turtles continue to lazily and over-confidently party, much to Splinter's dismay, as he orders them to be alert. The group soon learns that The Kraang have survived their previous attack, and a Kraang UFO is delivering a shipment of mutagen canisters to Shredder, who has teamed up with the Kraang to eliminate their mutual enemies.
While the Turtles successfully infiltrate the Kraang UFO and thwart this mission of the mutagen reaching Shredder, their inept incompetence causes a flurry of mutagen canisters to rain down on the city, much to their horror.
The Turtles struggle to contain an outbreak of mutations that occurs thanks to the leftover mutagen from the thwarted Kraang invasion. Kirby is among the victims of the outbreak, and a misunderstanding leads April to hate the Turtles and break off their friendship. However, the Turtles are able to earn her forgiveness when Donnie saves her from Karai, who has taken temporary command of the Foot while the Shredder is away in Japan resumes hunting her down with the help of The Kraang.
Having finally reconciled with the Turtles, April once again decides to seek shelter at their lair to undergo some more training with Splinter, while the Turtles continue searching for the missing mutagen but also be on the lookout for the Foot army.
The Hamato Clan also gains a new member when April's new friend Casey Jones helps repel an assault on the Turtles' lair. Kurtzman a scientist who has studied the Kraang for years , with the group learning more about the Kraang's backstory and why April is a crucial element to the Kraang's plot as well as the return and revenge of The Rat King who Splinter eventually defeats in the undercity , master Splinter confesses to the Turtles first Leo, than the other three the shockingly horrible secret about Karai's true identity he had been harboring, that she is his own long-lost birth daughter, and that she mistakenly believes that Splinter killed her mother, whereas it was really Shredder which is why she is filled with fanatical hatred towards them.
Meanwhile, The Shredder returns from Japan with the mutated Japanese bounty hunter Tiger Claw , who becomes the Shredder's new second-in-command, much to Karai's rebellious chagrin. During a battle with the Turtles, Tiger Claw is later sent through a portal inside a worm to the — animated series reality.
Additionally, Karai is informed of the truth about her life by Leonardo who became secretly smitten with her since they first met , however, she flatly distrusts Leo and harshly rebuffs this, even goes as far as brutally slaying the tortoise for his repeated "lies". But she is later shown eavesdropping on the group by hiding behind a billboard and overhears the group gossiping about her, becoming intrigued by their conversation.
Some time later, Kirby is eventually restored to his human form when Donatello finally manages to synthesize and concoct a Retro-Mutagen, which causes organic beings to reverse their major physical transformations, and help keep it away from former T. After Tiger Claw, who later returns to the reality, enlists her in a devious scheme to find the Turtles' lair, Karai succeeds in deceiving April, Donnie and Leo by pretending to trust them about Splinter.
She is taken to the lair, much to Raphael's ire. As the brothers argue, Karai sneakily schemes an ambush by slyly activating her tracking device, leading Tiger Claw to the lair. However, after she finally and genuinely does realize the truth herself thanks to Splinter showing her photographs of himself as a man with Tang-shen and Karai as an infant , her feelings towards Splinter and the Turtles especially Leonardo change.
Realizing the enormity of her treacherous schemes and cruelty towards the Turtles and Splinter, she joins forces with them and disowns Shredder and Tiger Claw for real this time by leading Tiger Claw to an old, underground meat processing factory. After the battle that ensues, she is captured by Tiger Claw, taken back to Shredder's lair where Shredder confesses the truth, and imprisoned. Repeated attempts to free Karai by Leonardo ultimately succeed, but the Shredder captures Karai again and uses her as bait to kill the Hamato Clan.
However, despite the best efforts from the Turtles and Splinter to rescue her once more, Karai ends up mutated into a feral and predatory purple-and-white serpent after her cage falls into a pool of mutagen containing snake DNA a trap that was meant for the Turtles , to everyone's horror. This goes against Shredder's plan, so he is contacted by Kraang Prime to propose a risky alliance and a solution. After negotiating, the two come to an agreement: Shredder and his forces will help the Kraang capture April and conquer all of New York City, and then the world in exchange for the Kraang robots helping Shredder capture and destroy the Turtles and Splinter, as well as restoring Karai back to her normal human form.
Over the next few weeks, the Turtles, April and Casey scour the city in search of Serpent Karai in the hopes of mutating her back to normal, but their search turns up nothing. Afterwards, Donnie must put aside his differences with Casey when some Purple Dragon gangsters steal and open an ancient Chinese dagger unleashing an evil ghost which tries to sap April's psychic powers while Leo, Raph and Mikey undergo an evil possession, becoming Ho Chan's henchmen.
When the Kraang perfect their previously unstable mutagen, the Turtles travel through a portal artificially made by Donnie into Dimension X, scouring this weird alien land and battle rock monsters to rescue Leatherhead, who is being tormented by his Kraang captors and sends a holographic distress message through an orb.
But only Mikey can figure this place out. They are successful in this mission, and escape back to Earth just before the Kraang's facility explodes, postponing their invasion for months in Dimension X time , meaning days in Earth time units. This gives the Turtles some more time to prepare their defenses, and Donnie some time to finish construction on the Turtle Mech. Although Splinter and the Turtles eventually fight off Kraang Sub-Prime, most of their lair is trashed, forcing them to abandon it.
A falling-out between Leo and Donnie jeopardizes the mission when Leonardo is accidentally and mistakenly separated from the rest of the team as more Kraang continue to invade, leading Donnie to lead.
Leo is left to single-handedly battle Shredder, Tiger Claw, Dogpound, Fishface and the entire Foot Clan army a hoard of Footbots but despite his valiant efforts, Shredder and his thugs gang up on the tortoise. Leo is gravely injured and knocked unconscious, as is Splinter after a battle with the Shredder, who, after defeating Leatherhead, ruthlessly flushes the unconscious rat down a sewer drain.
Meanwhile, Splinter is rescued by Serpent Karai, who recognizes him and is left on a ledge underground in the sewer to recover. Season 3 The group takes refuge at the O'Neil family's summer home upstate in Northampton , Massachusetts in order to recuperate from their loss at the hands of the Kraang and the Foot Clan.
Leonardo takes an extended amount of time to recover, but guided by an apparition of Splinter, is able to overcome his physical and mental wounds.
The group eventually returns to New York with the goal of finding Splinter, Karai, Kirby, and their other missing allies and liberate the city from the Kraang.
They are successful in finding Splinter who is completely feral , and, after restoring his humanity and memories, set up a temporary base in the abandoned Antonio's Pizza restaurant. Donatello begins work on new samples of retro-mutagen as the search for Kirby and Karai continues. Shredder later captures and mutates Anton Zeck and Ivan Steranko into his latest mutants a mutant warthog and rhino which Mikey dubs as 'Bebop and Rocksteady' after the duo are seen hunting down Serpent Karai while the Purple Dragons gain Hun as their leader.
The Turtles, after outwitting Bebop and Rocksteady, manage to spray some retro-mutagen on Serpent Karai but it has no effect. Slowly losing her mind, she bids farewell to the Turtles, April and Casey before escaping into the sea before getting captured by Shredder, who promises to restore her back to normal. Together, they manage to banish the Kraang back to Dimension X and free New York, but the effect of the invasion eventually earns Shredder cemented control of the city's criminal underworld for his efforts to create a mind-control serum meant for the turtles, Mutanimals and especially Serpent Karai, who gets brainwashed and begins hunting Splinter, the Turtles, April and Casey down.