In the comics, Arnold Flass is the corrupt partner of Jim Gordon. First appearing in Batman (vol.1) #404 (Feb. 1987) as part of the Batman: Year One storyline, Flass quickly grows tired of Gordon's "crusading" and, directed by Commissioner Loeb, "takes the boys to teach Gordon a lesson"
(a lesson Gordon returns before he and Batman bring Flass and Loeb to justice).
Michael Eklund previously played The Doll maker in Arrow.
Full name of Fish Mooney is revealed as "Maria Mercedes Mooney".