One of the big surprises of Gotham's first season was the death -- OK, make that "death" -- of mobster and nightclub owner Fish Mooney at the hands of her former umbrella boy Oswald Cobblepot. (If we've learned anything in three seasons, it's that a "watery grave" is hardly ever that.) Fish's body was recovered and stored at the Indian Hill facility beneath Arkham Asylum, where she was revived through the experiments of Hugo Strange, which imbued her with the ability to control those with whom she came in contact.
Escaping Arkham with some of her fellow Indian Hill test subjects, Fish hatched a plan to force Strange to create more monsters to form her new gang, and eventually left Gotham with him, ordered by Oswald not to come back. However she did return, and saved Oswald from Edward Nygma and his allies. They schemed to have Strange create an antidote to the Tetch virus ravaging Gotham, in hopes of forcing the city to pay a ransom, but Fish was accidentally killed by an infected Jim Gordon. Fish told Oswald with her last breath that she's died too many times already, something echoed by one of the show's producers, who said the character won't be back.
Introduced in Season 1 as the son of biology teacher Gerald Crane, inventor of an anti-fear formula, the teenage Jonathan Crane as conflicted about helping his father murder people using their worst fears. Jonathan was injected by his father with a serum that was intended to eliminate all fear. However, he overdosed and was last seen strapped to a hospital bed and hallucinating that he was being stalked and attacked by a monstrous scarecrow.
Crane is back with a vengeance in Season 4, clad in a Scarecrow costume drawn directly from the comic books, terrorizing all of Gotham with his scythe and fear gas, even as Oswald Cobblepot attempts to license crime in the city as part of his plan for a "Pax Penguina."
Ra's al Ghul
After all the buildup to the introduction of Ra's al Ghul, one of Batman's most formidable adversaries, his actual arrival was a little ... anticlimactic. Appearing largely in shadow in the final two episodes of Season 3, the Demon's Head urged a brainwashed Bruce Wayne to join him as his heir and manipulated him into stabbing a captive Alfred Pennyworth before revealing that the healing (and convenient) waters of a Lazarus Pit.
After some maniacal laughter and talk of a prophecy that Bruce would become his "knight in the darkness," Ra's disappeared, leaving the future Batman to his destiny -- at least for the time being. The Demon's Head returns in Season 4, undoubtedly to continue his manipulations from behind the scenes.
Returning Thursday at 8 p.m. ET/PT on Fox, Gotham stars Ben McKenzie as James Gordon, Donal Logue as Harvey Bullock, David Mazouz as Bruce Wayne, Robin Lord Taylor as Penguin, Cameron Bicondova as Selina Kyle, Erin Richards as Barbara Kean and Sean Pertwee as Alfred Pennyworth.