Jerome is depicted as a psychotic nihilist who spreads chaos in Gotham City until his eventual death, while Jeremiah is a cunning psychopath obsessed with tormenting Bruce Wayne.

In the series finale set ten years after Jeremiah's first appearance, Jeremiah is reinvented and becomes a figurative amalgamation of both Valeska twins over the course of the show, and while never officially adopting the name, becomes thematically representative of the Joker, complete with chemical disfiguration he applies white facepaint over, dyed green hair, red lipstick, dressed in a purple suit with a green undershirt and orange tie, as is the supervillain's traditional iconic appearance.

[6][7] A recurring theme on the show is how the Joker's ideology acts like a virus that can be spread through multiple characters, which executive producer Danny Cannon describes as "the opposite of Bruce Wayne, somebody who just wants to destroy... that could be anyone.

[13] Such a character named Jeri (played by Lori Petty) made an appearance in the episode "This Ball of Mud and Meanness",[14] running a nightclub catering to Jerome's sympathizers.

[18] In the fifth and final season, Jeremiah falls into a vat of chemicals, causing him to undergo another substantial transformation that alters his psyche into becoming what Monaghan describes as a "third character".

[22] During the virtual DC FanDome event in 2020, a documentary titled Joker: Put on a Happy Face was made to celebrate the character's 80th anniversary.

[25] He initially attempts to cover his tracks, but eventually laughs maniacally while admitting his actions to Detective Jim Gordon (Ben McKenzie) and medical examiner Leslie Thompkins (Morena Baccarin).

However, he did take inspiration from Mark Hamill's vocal performance in the DC Animated Universe, in addition to reading as many comics featuring the character as he could to prepare for the role.

Jerome returns at the beginning of Season 2, leading a team of Arkham escapees under the guidance of corrupt politician Theo Galavan (James Frain), who wants to spread fear in his plan to become mayor.

[27] During his reign of terror, Jerome murders GCPD captain Sarah Essen (Zabryna Guevara) and his own father, Paul Cicero (Mark Margolis).

[29][27] Introduced in Season 4 under the name Xander Wilde, Jeremiah is revealed to have been a child prodigy who was sent away by his mother after suffering severe abuse at Jerome's hands.

[30] Jeremiah is exposed to a variation of the Scarecrow's (Charlie Tahan) fear gas, which turns his skin chalk white and lips bright red, and he becomes a major antagonist in the series going forward.

[31] Jeremiah's torture of Alfred Pennyworth (Sean Pertwee) and crippling of Selina Kyle (Camren Bicondova) to torment Bruce are reminiscent of the Joker's defining actions in the graphic novel, Batman: The Killing Joke.

[33][34][35] In Season 5, Jeremiah grows more unhinged and flamboyant after his plan to turn Gotham into an isolated ruin succeeds,[36] with Monaghan taking inspiration from David Bowie and Tim Curry in his performance.

[38][39] This plan ultimately fails and Jeremiah falls into an experimental vat at the Ace Chemicals plant, referencing the Joker's most common origin story in the comics.

[41] Ecco (Francesca Root-Dodson) is Jeremiah's psychotic, utterly devoted henchwoman and the leader of the cult that worships him after Gotham becomes isolated from the rest of the world.

[45][22][7] He struggles to recall which of his memories from before his chemical accident are real, with his obsession with Bruce becoming so embedded that he pretended to be comatose for 10 years, waiting for him to return to Gotham after spending a decade abroad.

"[48] Screen Crush was heavily critical of both the show itself and Jerome's introduction, referring to it as a cheap selling point without any context intended to make the audience forget that Gotham is "absolute garbage television".

Club opined that, although Monaghan gave a great performance, Jerome embodied the show's flaw of ignoring set-ups and established plotlines in favor of introducing new characters and big 'reveals'.

[50] In contrast, Rob Bricken of Gizmodo felt that Monaghan did a solid Joker impersonation, referring to Jerome as an amalgam of the Jack Nicholson and Heath Ledger versions of the character.

[51] Screen Rant's Anthony Ocasio referred to the Jerome reveal as "the best scene the series may ever see" and stated that the show surprisingly succeeded in referencing the Joker, even though it felt out of sync with the grounded tone of previous episodes.

[52] Rolling Stone's Sean Collins praised Jerome's introduction and felt that the lack of an origin story was fitting because of the Joker's mysterious past in the comics.

[72] Den of Geek's Marc Buxton drew parallels between Jeremiah and the Batman: The Killing Joke and The Dark Knight Returns versions of the Joker, and found the character's narcissism compelling.