Magnificent Molecule Man as he appears in the video game.
The Magnificent Molecule Man was a character from the Goosebumps book, Attack of the Mutant. He was one of the henchmen of the Masked Mutant.
In the original book, he had only a minor role, as he was all part of a distraction plan the Mutant had set up for Skipper Matthews. He was disguised as the Mutant, and was melted by a molecule melter.