Baxter Stockman is a mad scientist and human enemy of the Ninja Turtles, becoming employed by Shredder in most incarnations. In the Mirage era, after creating the MOUSERS, with April O'Neil as his computer programmer, Stockman used them to commit strange bank robberies by allowing them to dig small tunnels leading into the vaults. April found out and tried to escape through the MOUSER factory elevator, but Stockman sent the elevator (with her still in it) down to the sewer level, where a squadron of MOUSERS were waiting to capture her. The Ninja Turtles saved her and successfully infiltrated the factory, stopping Stockman and leaving him in police custody. However, he escaped some time later and began using technology from DARPA to build a robot body for him to install his own brain into, making him a cyborg. Stockman tried getting revenge on the Turtles, but his new body was electrocuted and seemingly destroyed. Only his glasses remained. In the 1987 animated series, Stockman (voiced by Pat Fraley) was a misguided Caucasian inventor who tried building his MOUSERS for the Ajax Pest Control company, but was told that it would only run them out of business and was kicked out of the building. Watching the whole scene through security cameras, Shredder approached him, offering an even better job, which Stockman accepted. Shredder had Stockman create a master control device for the MOUSERS so that the Foot Clan could use them to destroy the Ninja Turtles. However, the Turtles destroyed these MOUSERS and found Stockman's name on one of them, thus leading them to confront him and escape in his van (which later became the Turtle Van). Though he was defeated and committed to an asylum, Stockman was later freed by Shredder when Krang withdrew Bebop and Rocksteady to Dimension X. Following various incidents made by the Turtles during his service in the Foot that all ended with him getting abused by Shredder, Stockman was tasked to accompany Bebop and Rocksteady through an unstable portal to Dimension X to meet with Krang. Krang saw no use in his scientific expertise and decided to kill him by tossing him into a mutagen-powered disintegration chamber, which instead mutated Stockman into a mutant housefly due to letting a housefly land on his clothes and get tossed into the unit with him. Krang informed Shredder about what happened to Stockman. Blaming the Turtles and Shredder, Stockman fled Dimension X to take his revenge but was convinced by Shredder that the Turtles alone were responsible for his mutation and took him back to the clan, promising to have him retro-mutated once they have the Turtles pay. (via Wikipedia)
