The President of the United States issues an emergency address on the situation in Gotham City. After the 8.6 earthquake destroyed what was left of the ruined city that the Joker briefly ruled over, the President declares the city a lost cause, "civitas non grata", no longer part of the United States. Harley is thrilled by this, and goes on a rampage through the city, gleeful at its fleeting lack of all hierarchies. Carried on a sled by her new hyenas Bud and Lou, Harley returns to the Gotham Mall with a kidnapped sushi chef named Takashi to cook for her crew.
While Takashi cooks with limited ingredients and lack of refrigeration, Ivy pulls Harley aside and asks her why she spent the entire three weeks since the Joker's demise partying rather than attempting to take over the city and fill the power vacuum. However, Harley's biggest aim is to have no one in charge at all, and is basking in the temporary anarchic glee rather than trying to compromise her utopian dream by taking over. Ivy warns her that there'll be consequences if she doesn't take charge, at which point two henchmen from The Penguin arrive to claim the mall.
In response, Harley angrily proclaims that "it's a post-dibs world" and that "nobody owns nothing", and although the goons try to attack her anyway, King Shark bites one's head off for sushi and scares the other away. Ivy then reiterates that the other villains will continue trying to take over indefinitely, at which point a trio of mobsters from Two-Face arrive to try to claim the mall as well. Frustrated, Harley then goes to Noonan's Bar and gives a speech inspiring the goons to rise up and overthrow their masters, as she did to the Joker, forcing the remnants of the Legion of Doom to band together for their own safety when their henchmen suddenly turn on them.
Two-Face, the Riddler, Bane, the Penguin, and Mr. Freeze all gather at Iceberg Lounge & Casino to deliberate on their situation, and decide that they desperately need their "goons" back to sustain their way of life. They then form a new league, the Injustice League, and send Harley an invitation. While that happens, Commissioner Gordon continues trying to signal Batman in vain, until suddenly Robin arrives and reports that Batman was in the Joker's tower when it collapsed. Demoralized, Gordon simply tosses a plastic jug of whisky at Robin and ignores his attempts to step into Batman's shoes.
Harley later arrives back at the Gotham Mall, her own plan having backfired as she was forced to fight five different former-henchmen trying to go solo. Ivy also complains that they went from "five assholes" trying to rule Gotham to "a thousand little assholes", and after that Lou brings Harley her invitation to the newly formed Injustice League. This disturbs Harley, who only wants chaos, but Ivy simply says "I told you so!" Harley then goes to the league's headquarters at Gotham City Hall, where the Penguin insists that "there's gotta be a hierarchy", painting himself in opposition to Harley's desire to deconstruct absolutely everything.
Mr. Freeze offers her a place in the new hierarchy to win her complacency, offering her a small island while the rest of the league take larger portions of "New Gotham" for themselves. Adamantly unwilling to accept any form of order or ownership, Harley simply smashes the table and their proposed map, refusing to join them, so Mr. Freeze stands up and turns her into a block of ice. She remains that way for two months, with her crew unable to properly organize themselves to lead a successful rescue mission. This allows the Injustice League to swiftly bring the rest of Gotham City under their control. Two-Face even takes over the last remnant of the Gotham City Police Department, and Bane turns some of them into henchmen which he sends after Commissioner Gordon. Afterward, Gordon is left utterly alone as his wife finally demands a divorce.
The Penguin ends up keeping Harley's frozen sculpture in his portion of Gotham, where he is treated like a king. At his party, he finds an odd new waiter with yellow teeth, but thinks nothing of it and continues to mingle. Meanwhile, King Shark and Doctor Psycho are disguised as a bartender, Poison Ivy is disguised as an anonymous guest, and Sy Borgman is disguised as a piano player. Sy then activates a smoke machine and begins loudly singing "happy birthday" to the Penguin while Doctor Psycho telekinetically drops Harley's sculpture to the floor beneath a table cloth, allowing them to walk out nonchalantly.
However, the Penguin soon dispels the smoke with his signature umbrella and notices their escape, suddenly calling his henchmen to apprehend them. They flee and end up cracking Harley's ice sculpture enough to free her face, at which point she begins to scream. King Shark and Clayface hold off the pursuing guards while Sy pushes Harley out and uses a torch to free her swinging arm, allowing her to join the fight. She then begins to laugh maniacally as her sculpture is used to crush henchmen, but the sculpture gains too much momentum and ends up outstripping her allies, leaving Harley right in the Penguin's hands.
The Penguin begins to taunt Harley but gets too close, allowing Harley to bite his nose off. Her sculpture is then knocked backward by the recoil, finally shattering on the ground and freezing Harley. Penguin, more concerned about his "beautiful nose" than the pain, dodges Harley's bat and sees it destroyed. He then fires several grenades at Harley from his umbrella, battering Harley with the blasts but not killing her. He then ends up surrounded by smoke once again but doesn't dispel it like earlier, and so Harley uses the confusing environment to echo her voice all around and confuse the Penguin. She then sneaks up behind him and stabs him in the throat with the splintered end of her broken bat, killing him.
Afterward, Harley seemed to think she was only frozen for two hours, but Clayface bluntly informs her that she'd been encased in ice for two months. It turns out that Clayface finally managed to develop a plan that succeeded in saving Harley because the others in Harley's crew only considered attempting his ideas when all of theirs ended in failure. However, Harley is only aggravated about Clayface's backstories and becomes even more distressed when Ivy reveals that the Injustice League finished carving up the city for themselves, establishing a new order. Becoming enraged, Harley admits that Ivy was right, that she should've taken over after all, and so she declares that she'll eliminate the entire Injustice League and claim Gotham for herself. Concurrently, Batman himself is found, alive.
Cast and Characters
- Kaley Cuoco as Harley Quinn
- Jason Alexander as Sy Borgman
- Lake Bell as Poison Ivy, Barbara, Cheryl
- Ron Funches as King Shark
- Tony Hale as Dr. Psycho, Man, Hench
- Christopher Meloni as Commissioner Gordon
- Alan Tudyk as Clayface, Two-Face goon, Manager
- James Adomian as Bane, Riddler goon, Penguin goon
- Andy Daly as Two-Face, The President
- Wayne Knight as The Penguin
- Alfred Molina as Mr. Freeze
- Jim Rash as The Riddler, Male nurse, Cop
- Jacob Tremblay as Robin
- Gotham City being declared no longer part of the United States and turned into a lawless wasteland after a disaster is inspired by the Batman: No Man's Land arc from 1999.
- The small mohawk that Mr. Freeze sports might be a reference to Holy Musical B@man!'s Mr. Freeze played by Jim Povolo when he to sported a small mohawk.
- Harley says "Sweep the leg, Johnny" after squishing some goons into a wall. This is a quote from Kreese to Johnny in 1984 movie The Karate Kid.
- The scene where Harley bites off Penguin's nose is a possible reference to the 1992 film Batman Returns, when Danny DeVito's depiction of Penguin bites off the nose of a mayoral campaign aide.