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The Masked Mutant is a supervillain and the main antagonist in the twenty-fifth Goosebumps book, Attack of the Mutant, as well as its television adaptation.


Attack of the Mutant

The Masked Mutant is an evil supervillain who has the power to turn into anything in order to defeat his enemies, which includes The League of Good Guys, led by the super fast Galloping Gazelle. One day he got bored of them and wanted a new challenge — a new foe for his stories. So, he disguised himself as a girl named Libby; on a bus ride, he meets Skipper Matthews, his biggest fan.

Skipper started noticing the mutant's building and how it would sometimes vanish. The comics started publishing issues with him in it. When one comic depicted The Galloping Gazelle tied up in the Mutant's HQ, so he went there to rescue him. He rescues him, but Gazelle's plan to trip up the Mutant failed, so he ran off when the Mutant turned into a leopard.

The Mutant reveals to Skipper that he is actually Libby, and that a light that had shone on Skipper when he first entered the headquarters turned him into a comic book character. Thinking fast, Skipper claimed that he was The Colossal Elastic Boy, and he can only be defeated by sulfuric acid. The Mutant turns himself into a wave of acid, which Skipper dodges. As a result, The Mutant is defeated because he can only change back when he turns into a solid object.

Video game

The Masked Mutant is bent on transforming the real world into a comic book. He has constructed a "Green Beam" machine that can convert people and buildings into comic book drawings. When the villainous Mutant encounters the player during the final confrontation, the player destroys a tank of "Slima-Bean Juice" behind him. He is drenched in the green ooze and starts sobbing, as he shrinks away into nothing. Everything affected by the Green Beam reverts to normal afterwards.

General information

Physical appearance

The Masked Mutant was a tall and powerful-looking man. He wears a dark blue and orange costume, cape and mask. In the video game, his suit is dark purple and yellow, and he has yellow lenses over the eye holes of his cowl.

When disguised as Libby Zacks, The Mutant appeared as a young girl with carrot-colored hair tied back into a single braid. Libby also had green eyes and light freckles on her nose.


The Masked Mutant acted in just the way the classic supervillain would act. He was deceitful and sadistic and he was really bent on world domination and he was the most fearsome supervillain ever created. He was very sneaky, considering that he was able to hide from The League of Good Guys with his power to transform into anything solid and he was always determined to annihilate his arch-enemies and he hated it when any of them interfered with his plans. Also, he was very capable of lying, and even added that it was one of his better qualities.

The Masked Mutant was always determined to find new faces, good characters and good foes for his stories (this could be an indication that he was bored with fighting the same arch-enemies over and over again, and wanted to find something new for what he thought was a good challenge.). But he would always be sure that it would be over for his new foes as well. The Masked Mutant may have been evil, but he had a tendency to underestimate his enemies, which led to his downfall.


The Masked Mutant was a comic book villain with the power to alter his molecular form to transform into any solid. There was a set-back, though. Once he transformed into any kind of liquid, he could not ever change back to his normal self. However, it's revealed in Goosebumps HorrorTown that he managed fix this weakness not too long ago.

In the TV adaption, the Masked Mutant can also teleport.

List of appearances


Television and film

Video games


  • "You're old, Gazelle. You're over the hill. It's time to retire ... permanently!"
  • "I'll try not to leave any squid marks"
  • "I can't let you leave. You belong here now!"
  • "Yes, I'm a liar! It's one of my better qualities. But I'm not lying this time. You're not real anymore"
  • "You're a comic book character. Just like me!"
  • "I'm gonna tear you into pieces, and then tear your pieces into pieces!"
  • "You tricked me! The great Masked Mutant tricked by a boy!"


Regional depictions

TV series



  • The Masked Mutant is a fictional comic book series created by Jimmy Starenko, a likely reference to real-life comic artist, writer and publisher Jim Steranko.
  • The Masked Mutant's actor, Scott Wickware, also voiced The Haunted Mask in The Haunted Mask II and played a Hard Hat Worker in Welcome to Dead House.
  • The Masked Mutant's voice actor for the audiobook, Townsend Coleman, is best known for voicing Michelangelo in the 1987 Teenage Mutant Ninja Turtles series. 
    • Coleman's voice in the audiobook is similar to the voice he uses for The Tick in the 1994 The Tick animated series.
  • In Horrortown, while disguised as Libby, it's revealed that the Masked Mutant knows how to play the flute.