When looking back at beloved long-running franchises, their initial justifications can be a bit silly. Some magic MacGuffin, alien experiment gone wrong, or interference from another dimension changes everything and plays into every character's story. For the Teenage Mutant Ninja Turtles, their central plot device is a shimmering green liquid known as Mutagen Ooze.

The Teenage Mutant Ninja Turtles came into popularity almost forty years ago. The franchise has undergone so many unique phases over that career that one fan can have a completely different experience than the next. One element that has been present in almost every iteration is the Mutagen Ooze, which is almost always the start of the story.

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Where did the Ooze Come From?

utrom-tmnt-2012 Cropped

The first iteration of the Teenage Mutant Ninja Turtles, the Mirage comics by George Eastman and Peter Laird, the Mutagen was the origin of the Turtles, Splinter, and others. It's reappeared in almost every other iteration of the story. In most examples, its origin is tied to the Utrom aliens and/or their front company, the Techno-Cosmic Research Institute or T.C.R.I. In many iterations of the story, the mutagen isn't an intentional creation. It's often a result of improper chemical waste. Multiple dangerous chemicals mix together to form a glowing green ooze which has wonderful effects on any living thing it touches. Beyond the broad strokes, there are various explanations for its origin.

The Mirage comics imagined the mutagen as a result of chemical waste. The Utroms crash-landed on Earth sometime in the 80s and worked tirelessly to get themselves to their home planet. The excellent 2003 cartoon follows that example almost exactly. The 2012 cartoon eschews the Utroms' quest to get home, instead imagining the ooze as a common material in Dimension X. They add that it only has its current effects when exposed to Earth's physics. The terms "mutagen" and "ooze" are used interchangeably in most versions of the story, but the more recent IDW comic draws a line between them with a new backstory. In that continuity, ooze is a natural resource in the Utrom home world that must be refined by human scientist Baxter Stockman into mutagen. The Utroms intended it to function as a super soldier serum, but it didn't work out. Frustratingly, the 1987 cartoon simply didn't explain the ooze's existence.

How Does Ooze Work?

teenage mutant ninja turtles - image from the nickelodeon show

The effects of the mutagen also vary based on the continuity. The original Mirage comics demonstrated that their mutagen increases the intelligence, size, and strength of any animal that is exposed to it. The 80s cartoon adds a bit of nuance by depicting what happens if it hits a human. A person exposed to mutagen combines on a genetic level with the last animal it had contact with. This version of Splinter, for example, is the combination of a man named Hamato Yoshi and his pet rat. Most versions of the ooze that have appeared since the original cartoon have used both interpretations of its power. The 2012 cartoon adds the detail that a human who hasn't recently interacted with an animal will likely be melted by the acidic goo. The most recent Rise of the TMNT cartoon added the need for DNA in almost every exchange and depicted its effect on plants.

How Does the Ooze Fit Into the Movies?

Donnie and Leo in Teenage Mutant Ninja Turtles 3

The 90s film trilogy has a completely different explanation for the ooze. The T.C.R.I. company, here renamed T.G.R.I., still accidentally create the ooze as a result of accidental chemical waste. However, this iteration of the story doesn't feature the Utrom aliens. This fits in with a very common 90s trend of "toxic waste" playing into larger narratives. In addition, the ooze has slightly different effects in the films. The ooze still has the usual effects on animals, but it now acts as a powerful performance-enhancing drug when given to humans. The films depict scientist Jordan Perry specializing the ooze for different cases, once intentionally reducing its intelligence-enhancing ability to create more subservient monsters. When Shredder consumes mutagen, it turns him into a hulking monster, not unlike Bane's Venom serum. He doesn't appear to be fused with any particular animal, he's just bigger and stronger now.

The ooze is a key part of almost every TMNT project. The Turtles and all their mutated friends need some sort of catalyst, and the ooze has been the go-to answer since the beginning. Arguably, over forty years and countless new iterations, the mutagen ooze has been the most consistent element of the narrative. Aside from the personalities of the four Turtles, it's the most common fixture. Its effects and origins might change a bit here and there, but the mutagen ooze is the key MacGuffin of every version of the Teenage Mutant Ninja Turtles story. Without the mutagen ooze, they'd just be Teenage Ninja Turtles, and who'd watch that?

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