Some TMNT stuff really isn't for little kids.
The M.O.U.S.E.R.s are robots created by Dr. Baxter Stockman and through this affiliation enemies of the Ninja Turtles. The robots are about knee high. They have a head with sharp teeth and two legs. Their jaws are strong enough to bite through steel.
The M.O.U.S.E.R.s appear in the IDW comics, where they were created from the outset by Baxter Stockman for military purposes. They were referred to by the acronym M.O.U.S.E.R.s, which stands for for, "Minefield Ordinance Unarming System Enhanced Robots". Stockman gave them to Old Hob to help him fight the Turtles and abduct Splinter. Hob used them to attack the family in their lair, forcing them to abandon their home.
He continued to construct M.O.U.S.E.R.s during his stay on Burnow Island, and used them to swarm those he considered his enemies, including the Turtles. Stockman later constructed a new variety of flying M.O.U.S.E.R.s along with flyborgs, which he used to sway Shredder into taking him on as an ally. He used a neural-communication helmet to send another army of the robots into the Turtles' second lair, focused entirely on killing Splinter. However, the robots are ultimately destroyed by Karai and a battalion of Foot Ninja.
The M.O.U.S.E.R.s reappeared in the aftermath of the Triceraton invasion, where April O'Neil convinced Stockman to use them to kill the Rat King's rats. The robots intervened during a battle between the Rat King and the Turtles, and killed the rats.
Stockman also constructed very large M.O.U.S.E.R.s, which could be used for security patrols. These were placed both in StockGen and on Burnow Island.