These days, most people consider Harley Quinn one of the pillars of the DC media empire alongside Superman, Batman, Wonder Woman, and the Joker. But unlike those other heroes and villains, Harley's existence doesn't even predate the '90s. Her dark and problematic relationship with the Joker may seem like a core part of comic book canon, but it may never have happened if not for a soap opera and a cartoon. And while many kids will remember growing up with the trickster, she wasn't even part of the main DC universe until 1999.
Since her debut on the small screen and her jump to comics, Harley has become one of the best-sellers on the page, and she's spun out into various films and TV shows, not to mention a controversial video game appearance. But it's been a rocky road for the former sidekick, one that's seen canceled comics and a whole lot of pain.
It wasn't until 1999 that Harley Quinn officially entered the main DC canon. As part of the "No Man's Land" event, Paul Dini brought Harley into the fold, telling an abridged version of her Mad Love origin and using the devastation of Gotham to spring her into action as the character we all know and love. Unfortunately, the Joker tries to do away with this version of his future sidekick, but Poison Ivy steps in to save Harley - and gives her superpowers in the process.
Back in the fray, the Joker and Harley eventually join forces and ride out the rest of the event as companions - kicking off their relationship in the DC universe proper.
After debuting in the main DC universe, Harley Quinn received her first solo series in 2001. Though it didn't last long, it detailed her rise from doctor to villain more clearly, delving into her obsession with the Joker and the viciousness he displayed towards her.
There's always been a lot of trauma packed into the colorful character of Harley, and it's this series that really laid the groundwork for future tales. The villain's duality was also explored, nicely setting up her slow turn towards heroism in later years.
During the first run of Harley Quinn, the villain finds her life over and her spirit pulled down to hell. After a short time in the underworld, she is able to escape and come back to Earth - but she lacks a body as a result.
Now a spirit, she spends her time causing even more chaos and inflicting much of it on Martian Manhunter. The story is a rather zany chapter that further illustrates how the great beyond isn't the end in comics.
Though Harley Quinn was a hit on the screen and in the comics based in the world of the animated series, things changed once she entered the main DC continuity. Her 2001 series went downhill fast, getting canceled in 2003 due to poor sales.
While a lot of factors go into the cancellation of a comic book series, Batman historian Chris Sims thinks it comes down to the difference between the cartoon and comics. Though Batman: The Animated Series could be dark, the Joker of the comics is far more cruel and had a massive body count and a history of despicable deeds. For Harley to love that version of the villain may have been a bridge too far for fans. Regardless, Harley wasn't gone for good, but she did take a bit of a hiatus outside of her more cartoonish adventures.