Otis Flannegan worked for the Gotham Sanitation Department as a rat catcher until he got involved in a street fight. A fatality was involved in the skirmish and Flannegan took the front of the blame. Otis was convicted of manslaughter then sentenced for a decade in Blackgate. During his imprisonment, Flannegan had an epiphany. Otis realized he had spent so many years ridding the city of its rodent infestation that he failed to see what was really plaguing the city. The citizens of Gotham were the real infestation and despite his services towards the city, Gotham still turned on him. Flannegan developed an affinity towards rodents and eventually released from Blackgate for good behavior.
Otis took his revenge on each city official who was involved at his trial sentencing but rather than killing them, he subjected each of them to psychological as well as physical torture for five long years. Due to Otis' intimate knowledge of Gotham's sewers, no one was able to find the missing city officials. Every lead went cold and the case was all but forgotten until Gordon gave the case to Batman.
Batman found the missing officials and put an end to Flannegan's scheme. Otis vowed to plague Gotham with his army of trained rats and take his revenge on the city. During his subsequent incarceration, Flannegan maintained his unique communication with a brood of loyal rodents. By communing with them, Flannegan developed a barter system in Blackgate and his rats would act as couriers. The rats would smuggle items or relay messages to other convicts by using the ventilation ducts within Blackgate's superstructures. Notably, he helped Bane organize an escape in this way. During the events of Batman: Cataclysm, Ratcatcher escaped with a group of other villains, including Cluemaster.
At the start of Infinite Crisis, the Ratcatcher is being aided by the homeless, as well as his rats. When he was discovered by the police, they tried to take him away. However, when one of the homeless (an OMAC in hiding) men tried to help Flannegan, he was knocked aside which triggered the OMACs activation. The OMAC identified Ratcatcher as a gamma level threat and vaporized him.
In the New 52 universe, Ratcatcher is seen alive and well. Ratcatcher now resides within the ruins of Gotham's subterranean underworld and is in league with Batwing's arch nemesis...Menace.
Powers and Abilities
Ratcatcher has the ability to control and communicate with rats. He also has great knowledge of Gotham's sewer system, as well as Blackgate prison's layout.
In the Batman movie, the Ratcatcher suit was included in Batman's trophy room in Wayne Manor.
Batman: Arkham Asylum
Although Ratcatcher isn't in the game, his equipment appears in the ventilation system of the Botanical gardens.