Baxter Stockman is a scientist and inventor in the employ of Shredder.
Enter the Fly (comic)[]
An error in calculations caused the destruction of a device that Shredder was counting on for his evil plans. Aggravated by Stockman's continual mistakes, he tosses the scientist through a portal into Dimension X, trading him for Bebop and Rocksteady. Inside the Technodrome in Dimension X, Krang quickly becomes annoyed with Stockman and has his robots toss the scientist into a disintegrator chamber. Unbeknownst to them, a fly had also entered the chamber. Rather than disintegrating the pair, the chamber instead cross-mutated Stockman with the fly and he emerged as a fly mutant.