Harley Quinn (Batman: Arkham City)

An Arkham Asylum psychiatrist assigned to treat the Joker, Dr. Harleen Quinzel instead became obsessively fixated on her patient, believing herself to be in love with him. She helped him escape confinement and took on her own criminal identity as Harley Quinn. She remained at the Joker's side during his painful recovery from the effects of Titan.

Batman: Arkham Asylum

 * See: Harley Quinn (Batman: Arkham Asylum)

After Arkham
Six Month's later, Harley has been incarcerated in a high security cell, believing the rampant rumors that the Joker is dying to be false. However her hopes are soon shattered when she overhears a conversation between some guards not only confirming the Joker's short lifespan but also a conspiracy to have him killed. With this she kills and replaces one of the guards planning to kill Joker and rescues him right in the middle of the attempt on his life.

With this she hijacks a supply boat and uses it to sneak into the recently completed Arkham City, setting up her and Joker's base of operations in a abandoned factory. According to Hugo Strange, Joker's inevitable fate is having a hard impact on her causing her to fall into a depression and adopting a increasing millitant approach. Later on she is shown helping Joker with his recruitment campaign screening a potential recruit Lester Kurtz, giving him his clown mask, and showing him to his room before he ran off.

Batman: Arkham City
"It would be a shame to get blood all over my nice new outfit. What do you think, Bat-brain, like it? What am I saying? Of course you do! Who wouldn't?"

- Harley during her first encounter with Batman

Harley Quinn has taken over many of the duties of leading the Joker's gang due to his illness and is more vicious and deadly than previously because of her anger regarding the Joker's health. Harley even supervised the kidnapping of Nora Fries, wife of Mr. Freeze. Shortly after Batman rescues Catwoman from Two-Face, Harley launches an attack on the Arkham City Medical Center and kidnaps one of the doctors, taking her to Joker's Funland in the old Sionis Industries compound, and also implies that the last doctor got executed for failure to find a cure. When Batman comes for her, Harley is watching over the doctor she kidnapped nearly be executed by Mr. Hammer for failure, until she declares a change of plans and has them execute the medic via the roller coaster. When Batman revealed himself and defeated her gang, she scolds Batman and later disappears into Joker's private office, sealing it behind her, although she also encounters Clayface-Joker and briefly mistakes him for the actual Joker before realizing her mistake, causing Joker to hush her. When Batman arrives, Harley is crying over the dead body of the Joker only to reveal that it was a trap and attacks Batman alongside Joker.

With Batman infected with the same poison that is killing Joker, Harley keeps an eye on the Dark Knight as he tries to save Mr. Freeze from Penguin. After his rescue and the creation of a cure, Harley steals it and returns it to the Joker. The Joker, feeling revitalized, starts acting like his old self again and resumes his love hate relationship with Harley. While pursuing Joker to retrieve the cure, Batman finds Harley tied up outside of Joker's office. Batman leaves her and continues after Joker. In actuality, she wasn't able to deliver the cure to the Joker, as Talia al Ghul had intercepted her and stolen it, as well as tying her up outside Joker's office before she could get the chance to deliver it.

Harley was present outside the Monarch Theatre as Batman carried the lifeless body of the Joker out of it and out of Arkham City. She gasped and dropped to her knees sobbing uncontrollably at the sight. It is implied by guards that she has taken over Joker's operations; nonetheless, her position is tenuous as many believe she would not last without the Joker's support and many members voice desires to defect from the gang or usurp her (some gang members even voice plans to rape her, implying her life is in greater danger then she realizes).

Harley Quinn's Revenge
Weeks after the horrific events of Arkham City, Harley Quinn reunits Joker's former gang after escaping from a pychiatric ward, meant for temporary imprisonment. Returning to the condemned site of the former mega prison, Quinn took the Industrial District under her control and redesigned the Steel Mill, Quinn's and Joker's former base of operations, into a mourning ground as she concocted her ultimate plan for revenge. When Commissioner Gordon and the GCPD arrived, the district was in lockdown and Quinn kidnapped several officers officers and dragged them to the mill as part of a trap for Batman.

When the Dark Knight arrived and rescued two of the officers, Quinn wounded Batman and locked him in an air-tight glass ball in a giant memorial for her beloved. Two days later, Robin arrived and began making his way at the docks and finds Batman's utility belt. Traveling deeper into the docks, Robin eventually comes face-to-face with Batman in the giant Joker shrine, and fights Harley and her henchmen to retrieve her key card to unlocking the ball keeping Batman captive. Returning to the shrine, Quinn unleashes a Titan-enhanced thug on Robin, who defeats it and frees the Caped Crusader. Harley then activates the next step in her plan; rigging the area with GCPD-stolen bombs, forcing Batman to hunt them down while Robin rescues the other police officers.

Realizing she's close to defeat, Quinn calls Batman back to the shrine where her final plan begins- activating the Wonder City mechanical guardians (stolen by the Joker during Protocol Ten) and watching from the ten-foot Joker structure the fight ensuing. Destroying the robots, the Dark Knight then heads for Harley Quinn, who, in her last, final step of revenge activates the bomb hidden in the Joker structure, planning to kill both Batman, Robin and even herself, to reunite her with her beloved.

Batman is able to get Quinn and himself to safety, but soon fears that Robin was caught in the explosion. Harley relishes in Batman's anguish and moves to stab him in the heart to finish her revenge, only to be knocked out cold by one of Robin's projectiles. Harley Quinn is once again arrested by Gordon while Batman leaves, still scarred from Talia and Joker's death, but Robin assures Gordon that Batman will be fine. With Harley's plans ruined, her gang is rounded up by the Gotham Police and Arkham City is finally, officially shut down for good.

Arkham City Profile: Dr. Hugo Strange
Harleen Quinzel

A.K.A Harley Quinn

The Joker's plaything and sometimes girlfriend, Harley Quinn was happy to leave Arkham Asylum so long as she could be with her 'puddin.' Her devotion to the Joker is admirable, but it is clear that his illness has laid a heavy burden on her as well. Her behavior has become evermore erratic and vicious, as she appears to be in a state of emotional metamorphosis, manifested by her change in wardrobe to a more militant, harsh appearance.

Dr. Hugo Strange: Side Note

Ms. Quinn’s behavior has become evermore erratic and vicious.

~ Dr. Hugo Strange

Trivia

 * If the player goes into Harley's office in the Sionis Steel Mill, they will see a pregnancy test next to her old outfit from Arkham Asylum. If they zoom in, it will show that the test is postive. Also, if the player finds this before the game ends, Harley will sing a version of "Hush Little Baby".
 * In "Harley Quinn's Revenge", it is hinted that she may not be pregnant after all, as there are dozens of the same tests scattered around the Steel Mill room reading a negative symbol.
 * A baby's cradle can also be seen in the center, cradling Scarface, now painted to resemble a young Joker, also implying Harley had planned for her child's arrival long before she took another test.
 * Through out the Steel Mill there are little statues of Harley holding a glowing ballon. If the player uses this they can hear her speak a message meant for Joker's thugs; however, the player is meant to destroy these as part of a Riddler challenge. If any remain following Joker's death they play a recording of Harley crying.
 * If defeated by Joker's thugs Harley's message will occasionally play instead of Joker's, and will be the only ones to play after Joker's death.
 * Batman Arkham City: Lockdown [iOS] adds Harley Quinn to the game, her level takes place in a new section of the city, the Industrial District.

Game Over Lines
thumb|right|300px|Harley Quinn's game over screens.
 * "Stupid little dead bat! Who's gonna save ya now?"
 * "I knew it. You're nothin' but a lightweight loser."
 * "You were supposed ta save Mr. J bat-brain."
 * "If you're dead, who's gonna save poor Mr. J?"
 * "Neh-neh-neh-neh-neh-neh."

Gallery

 * Harley Quinn (Batman: Arkham City)/Gallery