It's a simple fact of the universe: Batman is cool. He's got the suit, the martial arts, the millions of dollars worth of gadgets, but one of his key coolness factors are the villains he has to face. They can range from being tragic figures to silly gimmicky characters that Robin can beat on when Batman doesn't care. The best known of these characters is his arch nemesis, the Joker. The Clown Prince of Crime creates a stark contrast to Batman's Dark Knight image by being the loudest, most colorful, and most dangerous of all of Batman's villains. So, what could make this clown even more interesting? Give him a girlfriend/sidekick. Hence the birth of Harley Quinn.
Of all of Batman's villains, Harley Quinn is probably one of the least dangerous. Usually assisting her "Mistah J" in his evil schemes, she's usually either overlooked or quickly dispatched by Batman or his own sidekicks. But as a character, she deserves much more. Having grown up on the Batman Animated Series myself, I fell in love with the Joker's favorite henchgirl, with her bubbly, almost naive personality, big smile and giant hammer, she won me over instantly.
If you're not familiar with the character, you may be thinking back to The Dark Knight and Heath Ledger's Joker and wondering "Who on Earth would want to be his sidekick, much less date him?" The answer is as sad as it is brilliantly written. Harlene Qunzel (Comic book names, I know) was once a fresh young psychiatrist starting new at Arkham Asylum. Wanting to write a tell-all book about the super villains housed inside, she began working very closely with one particular inmate-the Joker. Seeing not only an opportunity to cause trouble but a chance to have some fun, the Joker began confusing and manipulating the poor girl during their therapy sessions, until she was convinced she was desperately in love with him. The cartoon says it was a break out, and the comics say it was during the earthquake in Gotham City (Don't ask, it's complicated), at one point though Dr. Quinzel ditched the sane world, donned a red and black suit, called herself Harley Quinn, and the rest was history.
What's really interesting about this character is how and where her psychosis runs. Where with Two Face you get a split personality disorder, or the Joker with just being beyond insane, Harley is basically just in a bad relationship where things have gone too far. It's something that a lot of people have either seen or been in, which makes it a lot easier to relate to. At different points in both the cartoon and comic she finds herself taking a serious look at her life and how the Joker truly treats her. As mentioned before, he doesn't really love her but just drove her mad for fun. He's usually seen as abusive, physically, emotionally and psychologically, and will happily use her as bait to lure the cops and Batman off his tail so he could get away, leaving her to rot in Arkham until he returns. The only times he seems to be happy with her is either when he needs her or when they're current scheme is going to plan. During Harley's brief moments of relative sanity, she's sometimes able to break away from him and try to have a different life, even if it's just teaming up with Poison Ivy or even Batman on occasion. But like any bad relationship, no matter what's happened in the past, she always goes crawling back to the Joker.
This dichotomy is sick and twisted, but it forms this weird romantic sense to it, like Romeo and Juliet or Bonnie and Clyde, like two criminals who fell in love due to their life of crime. It's a tragic love story in it's own sense of it. If nothing else, it gives you something to look at and say "At least we're not as messed up as those two, aren't we, dear?"
In the brilliantly written Batman: Arkham Asylum and Batman: Arkham City, Harley is portrayed as a much tougher character, exchanging her clown outfit for something a bit more revealing. In Arkham City, criminals loudly worry that if Joker dies Harley will take over and that she at times seems even crazier than the Joker. That's certainly a frightening thought, that Joker may have actually created something even worse than him through his games.
So there she is. Creepy, cute, romantic, or sad, however you see Harley Quinn you can't deny that she adds her own special brand of crazy to both the Joker and Batman's lives. She's the evil clown you can't help but love, in the relationship you can't help but watch.
P.S. In case you're wondering, that's me and my girlfriend Katie Ecker as Joker and Harley Quinn for Halloween. To answer your questions: No, we're not as messed up as they are; Yes we really are that cute; and No, you and your significant other can never be as cute as we were in that picture.