Warning! Spoilers for Man-Bat #3 below!
In one of her recent appearances, Harley Quinn's secret superpower may rival Marvel's Deadpool. Her awareness of her own "unreal story" in her own comic is one thing, but in the latest issue of Man-Bat, Harley reveals in her impromptu psychoanalysis of the disgraced Dr. Kirk Langstrom that she possessed an awareness that borders on breaking the fourth wall. Considering that has been Deadpool's shtick for years, one can only imagine what might happen if they were to ever meet in an inter-company crossover in the future.
When she made the choice to go from psychiatrist to supervillain, her time spent with her on-again/off-again boyfriend the Joker caused her mind to slip into new dimensions of insanity. Although years have passed since she left the Joker to find a life outside of him, her mental instability has allowed Harley to toe the line between anti-hero and villain. Being a long-time member of Amanda Waller's Suicide Squad, she returns to Gotham with the goal of capturing Kirk Langstorm's monstrous other half in hopes of "recruiting" him. Although Man-Bat survives long enough to defeat most of Harley's teammates, she gets the upper hand with the fellow Batman rogue allowing Harley Quinn to straps Man-Bat down to a couch instead of a prison cell in hopes of therapy helping with his current dilemma.
In Man-Bat #3 by writer Dave Wielgosz and artist Sumit Kumar, Harley interrupts Kirk's unconsciousness by calling his happy ending a deranged fantasy, pulling him back to the real world where Harley wants to talk despite Man-Bat's ferociousness. She calls out his hopes of curing his impending death and fixing his broken marriage with the help of the Man-Bat serum as fantasies, painting a bleak and realistic depiction of the events that would follow should he go down that road. Administering an antidote to change him back to human, Harley yawns as she's already seen this earlier which feels less like a criticism to Langstorm and more to the comics creators for using the same storytelling technique more than once.
This awareness and ability to break the fourth wall is something that became synonymous not only with Deadpool but other characters in DC Comics as well. When Wade Wilson's life was saved by the Weapon X program, the extremity of his new healing factor not only disfigured him but also drove his already fragile mind insane. Throughout the years, Wade has shown awareness that Deadpool is a comic book character and a willingness to share this insight and opinions with other Marvel characters who simply dismiss the claims as more of Deadpool's crazy talk. Harley Quinn has shown such awareness especially in the New 52 where she'd comment on current events within her own storylines or even pick fights with her creators. The fact that her ex-boyfriend, the Joker, has had similar moments of addressing the readers or audience with commentary or humor suggests that insanity may open characters' minds to new levels of consciousness that regular people can't, or choose not to, reach or understand.
The fact that Harley is making these references outside of her own comic strongly makes the case that her unique blend of psychology and psychosis may have given her a secret superpower that only Deadpool would understand. The fact that Harley has orchestrated this sit down to counsel and advise Batman's strangest villain, Man-Bat, on his actions, their potential significance and her advice on what to do next shows she's more than a giggling, violence-hungry clown but that deep down, she still wants to help people. As Harley Quinn helps Man-Bat escape Amanda Waller's clutches, one can only wonder if this somewhat useless yet entertaining superpower was just a fluke or something we'll see again.