Mutagen Monster
Teenage Mutant Ninja Turtles (1987 Cartoon) episode
Mutagen Monster Title Card.png
Season Code: 03
Episode: 24
Original airdate October 26, 1989
Written by Michael Edens
Mark Edens
Episode chronology
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"Casey Jones - Outlaw Hero" "Corporate Raiders from Dimension X"
Teenage Mutant Ninja Turtles 1989 Season
October 19, 1989 - December 22, 1989
List of Teenage Mutant Ninja Turtles episodes


  1. "Beneath These Streets"
  2. "Turtles on Trial"
  3. "Attack of the 50-Foot Irma"
  4. "The Maltese Hamster"
  5. "Sky Turtles"
  6. "The Old Switcheroo"
  7. "Burne's Blues"
  8. "The Fifth Turtle"
  9. "Enter the Rat King"
  10. "Turtles at the Earth's Core"
  11. "April Fool"
  12. "Attack of Big MACC"
  13. "The Ninja Sword of Nowhere"
  14. "20,000 Leaks Under the City"
  15. "Take Me to Your Leader"
  16. "Four Musketurtles"
  17. "Turtles, Turtles Everywhere"
  18. "Cowabunga Shredhead"
  19. "Invasion of the Turtle Snatchers"
  20. "Camera Bugged"
  21. "Green With Jealousy"
  22. "Return of the Fly"
  23. "Casey Jones - Outlaw Hero"
  24. "Mutagen Monster"
  25. "Corporate Raiders from Dimension X"
  26. "Pizza by the Shred"
  27. "Super Bebop & Mighty Rocksteady"
  28. "Beware the Lotus"
  29. "Blast from the Past"
  30. "Leatherhead: Terror of the Swamp"
  31. "Michelangelo's Birthday"
  32. "Usagi Yojimbo"
  33. "Case of the Hot Kimono"
  34. "Usagi Come Home"
  35. "The Making of Metalhead"
  36. "Leatherhead Meets the Rat King"
  37. "The Turtle Terminator"
  38. "The Great Boldini"
  39. "The Missing Map"
  40. "The Gang's All Here"
  41. "The Grybyx"
  42. "Mister Ogg Goes to Town"
  43. "Shredderville"
  44. "Bye, Bye, Fly"
  45. "The Big Rip-Off"
  46. "The Big Break-In"
  47. "The Big Blow Out"

1987 Season1988 Season1989 Season1990 Season - 1991 Season1992 Season1992-1993 Vacation in Europe sideseason1993 Season1994 Season1995 Season1996 Season

Mutagen Monster is a season 3 episode of the 1987-1996 series.


Shredder and a squad of Foot Soldiers wait in a train yard, ready to hijack two approaching trains full of dangerous chemicals. Shredder's plan is for Bebop and Rocksteady to switch the trains on the sidings, transport the chemicals to the Technodrome, and use them to create a new batch of mutagen. Unfortunately, Bebop and Rocksteady start arguing about who gets to throw the switches in the signal box, and inadvertently switch the trains onto the same track, resulting in a horrific head-on collision. Infuriated, Shredder drags Bebop and Rocksteady back into the Transport Module and returns to the Technodrome. He seemingly doesn't notice that the chemicals are mixing on their own, near a pen of cows.

The Turtles are watching television when Michelangelo comes in with a deep-dish pizza, and tries to change the channel. A food fight breaks out between him and Raphael, but is interrupted by April's coverage of the wrecked trains. Donatello realises that the chemicals are combining to create an impure form of mutagen, and that there's no telling what could happen to anyone or anything that gets exposed to it. Back in the Technodrome, Krang yells at Rocksteady and Bebop for botching the operation. Shredder tells Krang that he and the mutants will try again and not fail this time. The Turtles race to the scene, and discover that while April is a safe distance away, Vernon has gone to get close-up footage of the crash, putting him in danger of being exposed to the mutagen.

Fortunately, Vernon's shoes protect him from the mutagen, and he remains his usual self, but two bulls drink from the pool of mutagen, and instantly fuse into a single, gigantic bull with horn-like protrusions covering its entire body. Seconds later it mutates again, growing even larger and causing its two front legs to fuse into one. The Turtles arrive just in time to protect Vernon from any harm, but are at a loss as to how to deal with a creature with such immense size and strength.

Just then, Shredder returns with Bebop and Rocksteady in an attempt to salvage some of the chemicals, but Shredder decides that the mutant bull would be a vastly more valuable prize. Unfortunately, even he doesn't have any idea how to capture or control it, and after several fruitless attempts by both parties to catch it, the bull splits into two copies of itself. The sight of this is too much for Shredder, and he returns to the Technodrome again. Meanwhile, the two bulls work together to corner April, but crash into each other when they attempt to stamp on April and fuse back into one, bigger-than-ever mutant bull, which makes off for the city.

The Turtles return to their lair, and after a discussion with Splinter, Donatello realises that because the mutagen was impure, the bull's mutation is not stable, and that by placing it in an atom smasher they could break it down into the original two bulls.

Meanwhile, Shredder requests Krang's help in catching the bull, and Krang gives him a giant nose ring and a control device that will make the bull follow orders. However, because Krang (correctly) suspects that Shredder intends to double-cross him, he keeps a more powerful control device for himself. While Donatello sets up the atom smasher at the local university, the other Turtles predictably find that the bull is in a China shop, wrecking the place. Shredder returns to the surface, scaring the bull out of the shop, and the three turtles lure it to the university.

However, Shredder follows and has his own lure - a mountain of salt, which the bull stops to lick, and when it does so Rocksteady jumps out of the salt and inserts the control device into the bull's nose. Before Shredder can fully take control of the bull, April's van crashes into the salt truck and sends the control device flying into Bebop's hands. Bebop tries to control the bull himself, but only succeeds in steering it right into the building containing the atom smasher, which Michaelangelo activates, reducing the mutant bull into four ordinary bulls (two copies each of the original two bulls).

Shredder returns to the Technodrome cursing his luck once again, and Michaelangelo uses his knowledge of cowboy movies to steer the bulls safely out of the lab. At the end, April O' Neil gets cow-licked which messes up her hair and makes the Turtles laugh.



Home media releases





  • When the mutant bull was created, two bulls combined, but when it is separated at the end, four bulls are seen.
  • After Donatello and Raphael bring the bull towards a red tarp, Michelangelo is seen with Leonardo's colours.