Ironically, given the sometimes-spineless nature of the character, Oswald Cobblepot's rise and fall and rise again forms as much of the spine of Gotham as does Jim Gordon's meandering path to redemption and Bruce Wayne's path to becoming the Dark Knight. An undisputed master, and all-too-frequent victim, of the art of the double-cross, the once and future Penguin clawed his way from Fish Mooney's umbrella boy to crime lord to mayor of Gotham.
But Oswald spent much of Season 3 at war with Edward Nygma, his one-time ally and (unrequited) love interest turned chief rival. After a series of twists and turns, Cobblepot ended up once more on the edge of a Gotham pier, seemingly about to be murdered by The Riddler. But the ever-calculating Penguin outsmarted Nygma, leaving Victor Fries to turn his enemy into an ice sculpture -- the perfect centerpiece for the grand opening of the Iceberg Lounge, and a reminder not to allow love to cloud his judgment.
Ah, poor Edward Nygma. The awkward, lovelorn forensic scientist struggled against his darkest urges, only to become a murderer -- OK, serial killer -- and a master manipulator who now prefers to be addressed as The Riddler (for the record, Oswald Cobblepot refuses to call him that). Allying himself with Cobblepott, Nygma helps him to get elected as mayor of Gotham, and is named as chief of staff in return.
It's likely their partnership was doomed from the start. However, it's jealousy that tore it apart, as Cobblepot ordered a hit on Nygma's girlfriend, which became a declaration of all-out war -- with Nygma, Barbara Kean, Tabitha Galavan and Butch Gilzean on one side, and Cobblepot, Ivy Pepper, Victor Fries and Bridgit Pike on the other. Just when it seemed Nygma would rid himself of Cobblepot for good at the end of Season 3, the tables were turned, and Nygma was left as nothing but frozen decor for the Iceberg Lounge. Odds are, he won't remain on ice for long, though.
Gotham is frequently cruel to its residents, and there's perhaps no greater testament to that than Barbara Kean, wealthy gallery owner and ex-fiancée of Jim Gordon turned Arkham Asylum inmate and gangster. As if attempts on her life weren't enough, she became romantically involved with a man who turned out to be a serial killer, who kidnapped and brainwashed her, then forced her to murder her own parents. Psychologically shattered by the experience, she was incarcerated in Arkham Asylum, only to escape as part of a botched attempt to kill Jim that ended with her in a wedding dress, and in a coma.
Later released from Arkham by Hugo Strange, Barbara opened The Sirens nightclub with business and romantic partner Tabitha Galavan, and the two join with Edward Nygma and Butch Gilzean to destroy Oswald Cobblepot's criminal empire, with the intention of her becoming queen of the underworld. At the end of Season 3, she seemingly killed Butch -- of course, we know he's coming back in a different form -- after learning that he and Tabitha were plotting to betray her. In turn, Barbara was electrocuted in a fight with Tabitha and (again) seemingly killed. However, Barbara is depicted on the Season 4 poster and, briefly, in the latest trailer, so apparently that didn't take.
Butch Gilzean (aka Cyrus Gold)
One of the biggest twists of the Season 3 finale wasn't the shooting of Butch Gilzean by Barbara Kean, but rather the subsequent revelation that the mob enforcer's real name is Cyrus Gold, better known to DC Comics fans as Solomon Grundy. Shot point-blank in the head, the longtime henchman (first to Fish Mooney, then to Oswald Cobblepot and, finally, to Barbara) was left comatose, laying the groundwork for him to return as the super-strong zombie.
Gotham's producers have made no secret that's going to happen in Season 4, and in spectacularly comic book fashion: When Gotham General Hospital needs to free up beds, administrators simply dump the vegetative Butch into Slaughter Swamp. He'll reemerge from its murky waters in a new form, and with a new (and unlikely) ally: Edward Nygma.
During a season in which Gotham's proto-Joker Jerome had his face removed, reattached, and then literally punched off by Jim Gordon, the aging of Ivy Pepper still may be the weirdest, and potentially creepiest, development. Introduced in the pilot as an abused child, she was orphaned when her mentally unstable father was shot dead while attempting to kill Jim, and her mother committed suicide shortly thereafter. A friend and ally of Selina Kyle, Ivy encountered Bruce Wayne's doppelganger, subject 514A from Indian Hill, and ran afoul of a resurrected Fish Mooney, who feared the girl would reveal her plans. Fish ordered fellow Indian Hill escapee to use his aging power to kill Ivy, who escaped but fell into a drain pipe and was swept away by the current.
However, Ivy emerged from the water as a fully grown woman. She later revealed herself, in her new form, to Selina, and rescued Oswald Cobblepot after he was shot by Edward Nygma and thrown off a pier. After nursing Oswald back to health, she helped him to recruit "an army of freaks," Victor Fries and Bridgit Pike, so he could exact revenge. At the end of the season, Ivy went to the aid of an injured Selina, and used her plants to heal her friend following her encounter with 514A, and helped Oswald to develop the Iceberg Lounge.