Mutagen, also known as Retromutagen Ooze, is a mucilaginous substance that has served as a key plot device in nearly every medium of the Teenage Mutant Ninja Turtles. Any creature that is exposed to mutagen will rapidly increase in size, strength and intelligence (sometimes), and even gain superpowers. It is responsible for mutating, among others, Splinter and the four (or five or six) Ninja Turtles, and villain pairings such as Bebop & Rocksteady or Tokka & Rahzar or Dogpound & Fishface.
The mutagen was depicted slightly differently in this cartoon; rather than causing its victims to increase in size, it caused them to transform into a hybrid of their original species and whatever creature they have most recently been in contact with. It was revealed in the episode "Invasion of the Punk Frogs" that the mutagen can be made mixing nyotrinaline with Taxon-9. In the episode "Enter: Mutagen Man", a third ingredient was mentioned - Bindex3. In the episode "Shredder & Splintered" it's acidic. It is also responsible for creating many of the show's mutants, such as Bebop, Rocksteady, the Punk Frogs, Leatherhead, Slash, Groundchuck, Dirtbag, and Mondo Gecko, to name but a few.
2003 SeriesThe mutagen was created by the Utroms while they were trying to create a machine that will allow them to escape Earth after they crash-landed on it. Disguised as T.C.R.I., they tried to create the machine secretly. However, during its creation, the waste turned into a mutagen, with their attempts to dispose of it resulting in a canister falling off the back of a truck and mutating the turtles and Splinter when it fell into a sewer and splashed all over them. Much like in the Mirage Comics, the mutagen causes explicit growth, both physically and intellectually. Among the victims were the turtles, Leatherhead and Splinter.
2012 SeriesIn this series, the Mutagen is depicted as having several similar properties to the version seen in the 1987 series; It blends with the victim's genetics with that of whatever creature they have last made contact with. It has a glowingly blue/green coloration to it. Michelangelo occasionally refers to it as 'mom' in this cartoon, due to the role that it played in their creation, while Hamato Yoshi's human DNA was ultimately responsible for the humanoid form that they took on. The Mutagen also seems to have the ability to merge organic substances and inorganic substances, as seen with Spy-Roach, and the same subject shows that it can also cause similar effects to the original comic version, both increasing size and intelligence (sometimes). However, Parasitica shows that this isn't always the case...
As seen in "The Pulverizer Returns!", if a human has not come into contact with an animal or plant before being effected by Mutagen, their bodies will be molecularly broken down, turning them into a pile of acidic goop, with only their internal organs still remaining and intact...Pulverizer also states that the Mutagen burns a lot.
It has been stated that the Mutagen was not intentionally created as a mutative agent; It apparently had a different property or two when it was created in the Kraang's home dimension, but the new laws of physics in this plane of existence (our dimension) altered it's function. It was shown in The Manhattan Project that the Mutagen is a natural by-product of massive, worm-like creatures known as Kraathatrogons.
As opposed to being labeled T.C.R.I. (Techno Cosmic Research Institute) in the Mirage comics, the canister in which the ooze is kept is written as "T.G.R.I." (Techno Global Research Industries), in compliance with the plot. In the first film, the mutagen is shown as having been the substance that mutated Donatello, Raphael, Michaelangelo, Leonardo, and Splinter from ordinary animals into anthropomorphic beings.
Mutagen was a much more integral part of the second movie, Teenage Mutant Ninja Turtles II: The Secret of the Ooze. Having identified TGRI as the source of the Ooze, the Foot Clan abducted Professor Jordan Perry and forced him to create a new batch of ooze, to create new warriors against the turtles. This mutagen was used to mutate a wolf cub and a baby snapping turtle into Rahzar and Tokka, respectively (Although Professor Perry was able to modify the new ooze to retard the subjects' intellectual capacities, both creatures being relatively infant-like where Splinter achieved human-level intellect fairly quickly and the turtles were only limited by their initial youth).
Near the end of the film, Shredder drank some mutagen to become Super Shredder. It is unknown what, besides his natural human form, animal species' attributes the Shredder gained during this time. Jordan Perry explains to the Turtles that the ooze that mutated the Turtles and Splinter was a mistake. In Perry's words, "an unknown mixture of discarded chemicals was accidentally exposed to a series of radiated waves", results in the creation of the ooze which has "remarkable, but dangerous mutagenic properties." Donatello was very disappointed and upset upon learning this, as he always hoped that there would be more to their origins than an accident, but Splinter encouraged him not to judge his worth based on his origins.
In Turtles Forever, there were small capsules of what appeared to be purple mutagen which Donatello took possession of from the 1988 Shredder. At least two members of the Purple Dragons were mutated by the mutagen. The first was Mohawk, who was mutated into a half-dog mutant, while Hun was mutated into a half-turtle which was similar to Slash. A great deal of mutagen was mass-produced by Ch'rell and Karai. They used it to mutate human foot soldiers into a mutant army which they used along with upgraded robot 1987 Foot Soldiers in the foot's attack on New York in the 2003 universe.
IDW's mutagen has special properties outside of creating mutants; it has healing and transformative properties on its own. Takeshi Tatsuo was healed by it to the point where he was able to regrow a foot, and it kept him youthful when ingested. The mutagen was integral in the resurrection of Oroku Saki and Kitsune. Mutagen was also given to Arnold Jones to restore his long-lost muscle. Among the victims were the turtles, Splinter, Old Hob, Slash, Flyborg, Traag, Granitor, the Rock Soldiers, Bebop, and Rocksteady.
In the episode "Shredder & Splintered", it was mentioned as a neutralizer for the mutagen. Later in the series it appears to be Compound X7, a rare experimental anti-mutagen.
In Teenage Mutant Ninja Turtles II: The Secret of the Ooze, it was mentioned that the neutralizer is made of dimethyl chloride and must be heated to 338 Kelvin (65° Celsius or 149° Fahrenheit), which must be consumed in order to be effective; the turtles were able to trick Tokka and Rahzar into taking the anti-mutagen by freezing it into ice cubes and hiding the cubes in doughnuts.
Currently in the 2012 TV series, Donnie is trying to create an antidote to cure those who came in contact with the mutagen, specifically Timothy and Kirby O'Neil.
In the first Teenage Mutant Ninja Turtles GBA game, Mutagen canisters are used as health items.