The Teenage Mutant Ninja Turtles (TMNT or Ninja Turtles) are a fictional team of four anthropomorphic turtle mutants, who are trained by their sensei, Master Splinter, to become skilled ninja warriors.

The Teenage Mutant Ninja Turtles (TMNT or Ninja Turtles) are a fictional team of four anthropomorphic turtle mutants, who are trained by their sensei, Master Splinter, to become skilled ninja warriors. From their home in the sewers of Manhattan, they battle petty criminals, evil megalomaniacs, and alien invaders, all while remaining isolated from society at large.

The TMNT originated in an American comic book published by Mirage Studios in 1984. The concept arose from a comical sketch by Kevin Eastman during a casual evening of brainstorming with his friend Peter Laird. Using money from a tax refund together with a loan from Eastman's uncle, the young artists self-published a single issue comic intended to parody two of the most popular comics of the early 1980s: Marvel Comics' The New Mutants, which featured teenage mutants, and Frank Miller's work on Daredevil, which featured ninja clans dueling for control of the New York City underworld.

Much of the Turtles' mainstream success is owed to a licensing agent who sought out Eastman and Laird to propose wider merchandising opportunities for the offbeat property. In January 1990, they visited the offices of Playmates Toys Inc, a small California toy company who wished to expand into the action figure market. Accompanied by the popular Teenage Mutant Ninja Turtles animated series, the TMNT were soon catapulted into pop culture history. At the height of the frenzy, the Turtles' likenesses could be found on a wide range of children's merchandise, from PEZ dispensers to skateboards, breakfast cereal, and school supplies.

Today, there is a resurgence in the Turtles' popularity with the success of the recent animated series, a new line of Playmates action figures, Konami video games, and a new computer-animated feature film in production for a March 23, 2007 release.

Leonardo - The de facto leader of the Turtles, Leonardo is courageous, decisive, and a devoted student of martial arts. As a strict adherent to Bushido, he has a very strong sense of honor and justice. He wears a blue mask and wields a pair of katanas. He is named after Leonardo da Vinci
Raphael - The team "anti-hero", Raphael has an aggressive nature and seldom hesitates to throw the first punch. His personality can be alternately fierce, sarcastic, and full of angst. He wears a red mask and wields a pair of sai. He is named after Raphael Santi.
Michelangelo - The easy-going and free-spirited Michelangelo provides much of the comic relief. While he loves to read comics and eat pizza, this Turtle also has an adventurous side. He wears an orange mask and wields a pair of nunchaku. He is named after Michelangelo Buonarroti.
Donatello - The brilliant scientist, inventor, and technology geek, Donatello has a reputation as something of a wise guy. He is perhaps the least violent Turtle, preferring to use his intellect to solve conflicts. He wears a purple mask and wields the bō. He is named after Donato di Niccolò di Betto Bardi.
Splinter - The Turtles' sensei and adoptive father, Splinter is a mutant rat who learned the ways of ninjutsu from his own master, Hamato Yoshi. Splinter's name is a parody of Stick, the man who mentored Daredevil.
April O'Neil - A former lab assistant to the mad scientist Baxter Stockman, April is the plucky human companion of the Turtles. She embarks on many of the Turtles' adventures and aids them by doing the work that the Turtles themselves cannot do in public. During the early height of TMNT popularity, April was famously depicted as a television news reporter.
Casey Jones - A vigilante who has become one of the Turtles' closest allies, Casey fights crime with an assortment of sporting goods (baseball bats, golf clubs, hockey sticks, etc.) while wearing a goalie mask to protect his identity.
Shredder - A villainous ninja master named Oroku Saki who, along with his evil Foot Clan, is the arch-enemy of Splinter and the Turtles. Shredder wears a fearsome suit of armor covered with sharp blades. Also, in many of the earlier, less comic-oriented cartoons and films, Oroku Saki is directly responsible for both the mutation and the death of Hamato Yoshi.
On December 10, 1987, the Teenage Mutant Ninja Turtles' first cartoon series began, starting as a 5-part miniseries and becoming a regular Saturday morning syndicated series on October 1, 1988 with 13 more episodes. The series was produced by Murakami-Wolf-Swenson Film Productions Inc. Mirage Studios does not own the rights to this cartoon series, so changes made in the 1987 version of the TMNT have not translated to other versions. Here, the Ninja Turtles are portrayed as four wise-cracking, pizza-obsessed superheroes who fight the forces of evil from their sewer hideout, and make their first appearance in masks color-coded to each turtle, where previously they had all worn red. The cast included new and different characters like Bebop and Rocksteady and the Neutrinos. Original characters like Splinter, Shredder and the Foot Soldiers stayed true to the comics in appearance and alignment only. Instead of being Hamato Yoshi's mutated pet rat, Splinter was a mutated Yoshi himself. The Foot Soldiers changed from human ninja to a endless supply of robotic grunts, allowing large numbers of them to be destroyed without anyone dying. Krang, one of the series' most memorable villains, was inspired by the design of the Utrom, a benevolent alien race from the Mirage comics. The animated Krang, however, was instead an evil warlord from Dimension X. Baxter Stockman, whose race was inexplicably changed from African American to White American, was rewritten as a shy and meek lackey to Shredder, later mutating into an anthropomorphic housefly.

Starting on September 25, 1989, the series was expanded to weekdays and had 47 more episodes for the new season. There were 15 new syndicated episodes for the 1990 season. There were also the 13 "Vacation Europe Episodes", which did not air until USA Network started showing reruns in late 1993, most likely because of animation or schedule problems.

On April 21, 1990 a drug prevention television special was broadcasted on ABC, NBC and CBS named Cartoon All-Stars to the Rescue that featured some of the most popular cartoons at the time; representing TMNT was Michaelangelo.

Starting on September 8, 1990 (with a different opening sequence), the show began its run on CBS. The CBS weekend edition presented a full hour of Turtle Power, initially airing a couple of Saturday exclusive episodes back to back.

On September 17, 1994, (with a different theme song, opening sequence, and end credits background) the series continued with one episode per week, but big changes were made to the series. Starting with the 1994 season, the format of the series was changed to a more action-oriented show, removing many character building scenes and the cartoon feel of the series. The opening sequence was completely changed to one where clips of the 1994 Season were used instead of animation specifically for the intro. The theme song was changed to a techno beat and scenes from the 1990 live action movie, Teenage Mutant Ninja Turtles were intercut with new scenes from the 1994 Season. The sky was changed from a blue sky to a red sky with gray clouds to give the show a darker tone, similar to what was done with the original Spider-Man animated series in seasons 2 and 3. The series ran until November 2, 1996 when it aired its final episode. Its enormous popularity gave rise to numerous imitators, including the Battletoads, Cheetahmen, Street Sharks, and Biker Mice from Mars.

The first 66 episodes are currently available on DVD.

In 1997-1998, the Turtles starred in a live-action television series called Ninja Turtles: The Next Mutation that follows the events of the movies. A fifth turtle was introduced, a female named "Venus de Milo" who was skilled in the mystical arts of the shinobi. The series seemed to be a loose continuation of the movie franchise, as Shredder had been defeated and the Ninja Turtles encountered new villains. Other connections to the feature films include the fact that Splinter's ear was cut, the Foot Soldiers were humans, and the Turtles lived in the abandoned subway station seen in the second and third movies. The Next Mutation Turtles even made a guest appearance on Power Rangers: In Space, a live-action show that was popular at the time.

However, The Next Mutation never caught on with fans, and it was canceled after one season of twenty-six episodes. Since its cancellation, the program has been considered apocryphal by most of the TMNT fanbase, and Peter Laird has disavowed all knowledge of the character Venus de Milo, while Kevin Eastman is more open to talk about her.

On February 8, 2003, the Fox Network revived the Teenage Mutant Ninja Turtles franchise with the help of 4Kids Entertainment as a Saturday morning cartoon in the "FoxBox" programming block, which has since been renamed "4Kids TV". The 2003 TMNT cartoon series is produced by Mirage Studios, and Mirage owns one-third of the rights to the series. Mirage's significant stake in creative control results in a cartoon that hews more closely to the original comics, creating a darker and edgier feel than the 1987 cartoon, but still remaining lighthearted enough to be considered appropriate for children