|“||I can't let you leave! You belong here now!||„|
|~ The Masked Mutant|
|“||You tricked me! The great Masked Mutant tricked by a boy!||„|
|~ The Masked Mutant's last word before his demise|
The Masked Mutant is the main antagonist in the Goosebumps book Attack of the Mutant.
He is an evil supervillain who can change his molecular form into any solid material. He is constantly opposed by a league of superheroes led by the Galloping Gazelle, the world's fastest man. Although the Masked Mutant took a form of a young girl around Skipper's age, he is defeated in the end when Skipper tricks him, pretending to actually be a real kid superhero called the Colossal Elastic Boy.Skipper told him that his "weakness" is acid, so the Mutant decides to shapeshift into Skipper's "weakness". However, Skipper knew the Mutant's weakness- if the Mutant shapeshifts into a liquid material, the Mutant would be permanently locked him in that form and, in a sense, would die.