Harold Allnut was a mute, autistic and hunchbacked man. He was also an expert mechanic. Harold was at one time fooled by Penguin into having him create weapons. He created various weapons of mass destruction which Penguin planned to use to kill Lew Moxon and start a gang war. Harold built Penguin one final weapon to kill Moxon with but Batman convinced him to betray Penguin which he did. Penguin tried to kill Harold however; he was saved by Batman. Batman then allowed Harold to stay in the Batcave. After the arrival of Bane, Harold helped Bruce Wayne and Alfred build the JPV Battle Suit so Bruce could fight Bane. Sometime later Bruce Wayne set Harold up in a mechanic shop and would help Lucius Fox develop new weapons for Batman.