Whilst this was a “Gotham Girls” team-up, it most definitely was not in the vein of the playful and pally flash animated series!

No, in keeping with the grittier and more adult tone of the mainstream comics, Gotham City Sirens found the ladies in a tense truce, banding together for survival's sake in the aftermath of a Gotham without THE Batman!

Gotham City Sirens, typically, divided fans.  Whilst many were initially delighted that the series was being penned by Paul Dini -  not only one of the most acclaimed contemporary writers of Batman lore, but the very same dude who had a major hand in creating Harley - after a few issues some fans felt his treatment was glib and superficial and not delivering what they had initially hoped for. With no announcements and to many fans' confusion, the writer changed soon after as did the artist and by the end of its run, GCS had changed creative teams several times, to varying success. This made the timbre of the book inconsistent and its direction unclear.

When the book was just three issues in, in addition to these first thoughts, I wrote the following about the characterisation of Harley:

I do find it fascinating to watch the way Dini has developed Harley over the years, particularly how he brings different aspects of her more to the fore depending on the setting. Her playfulness and sweetness are played up in B:TAS, her wickedness and malice in the new Arkahm Asylum VG, her ambition and calculatedness in The Batman. 
Mainstream canon offers the opportunity for a fully balanced integration of all the varying elements of her and this is the approach he seems to take – and is continuing with so far in GCS. 
In just two issues we've seen so much of her peeking out: playfulness, genuine disingenuousness, hedonism, enthusiasm and flightiness - right alongside her callousness, canniness and manipulativeness. She was definitely playing up the bimbo schtick which I love to see her do. She's a beautiful bimbo, is our Harley, and thoroughly genuine about it - but she knows how to work it to her advantage - or just to her amusement - too. 

These stories were carried out with varying degrees of success and with varying responses from fans.  What initially delighted fans with the promise of JokerxHarley goodness in the Gaggy story turned out to be a gut-wrenching, heart-plucking disappointment as Gaggy's deceit was revealed. Boringly, Dini seemed to be placing the blame for Harley's obsession with the Joker on a bad relationship with her father, about which I had the following to say:

For the whole lot reduces the grand tale of Harley's path to madness – the enormity of what she gave up for love is undermined by her family's easy acceptance of her chosen lifestyle. What exactly were the stakes for Harley in becoming a supervillain? She was accustomed to growing up surrounded by crime with a mother who constantly welcomed everyone back. What transformation did Harley go through exactly then? This story would have you believe there was never any difference between the identity of her former life and who she is now. So where the hell has the pathos gone – that pathos inherent to the story of an ambitious and, if morally questionable at least sincere and passionate, young doctor who wanted to make something of herself only to become more than she could ever dream possible – to completely upend a life she then wishes she could reclaim????

This was said of much of the series, regardless who the character focus was for whichever story arc. In the end. GCS was unsatisfying for many different reasons and an inconsistent and glib treatment of character with uninspiring storylines was often cited as being at the heart of it.  A series that had so much potential ended up being a middling success. And in the final bittersweet blow, they gave us a reunited JokerxHarley only for the series to be cancelled and the characters split up again for the New 52.

A quick reflection of what I wrote about GCS when the series was still new:

After a standard of several years standing of lacklustre mainstream treatment, could Harley finally be given her dues? After all, who better to handle her than her Daddy? The guy who understands her better than anyone? Several times he's tried to put her on the right track, depiction wise, by leaving trails other writers could pick up and follow – only for them go meandering in some other direction. Now that he has full reins once more, will he finally establish Harley properly within the mainstream canon?
So far, the outlook is good! Only three issues in (and only two of them written by him, incidentally) at time of this writing and the story is off to a slow start but character-wise, there's enormous promise in there!
So far the outlook is good – great, even! But at this early stage of the game, it's hard to tell! It may all go horribly wrong!

Initially, while I very much defended the characterisation of Harley in Dini's hands, it began to provoke me by seeming to be quite shallow after all... at first it made sense that a Harley without purpose as given to her by the Joker would be an unproductive layabout, waiting for some direction. But as the series continued on, this began to nag - a good storyline could've concocted some purpose for her. It was good, initially, for the point to be made that Harley is a willing number two and that being separated from the Joker isn't automatically going to unleash her fearsome, independent, assertive side, as so many against the ship argue. But for the whole series to be that way? It took fans dedicatedly emailing DC with our desires to see a reunion between Joker and Harley for her to be given something to really work with. And even then aspects of it felt contrived and OOC - for both HQ & J. 

Furthermore, the relationship between the series' three stars did not always make sense. What began as an uneasy truce became way more affectionate than it should ever have between these characters. Whilst it climaxed with a split and the return to the old animosity, it too quickly moved into sisterhood... particularly between Catwoman and Harley who, due to their respective relationships with Batman and the Joker, would never have formed a close bond. Selina, in particular, would keep her distance from Harley out of awareness she's unapologetically attached to the man who has caused Bruce the most grief. It does make sense that in the weird, wild world of Gotham that, over time, they would've formed some sort of closer relationship that would inevitably be broken, but I felt it happened too easily and without any real care being taken to depict how the pressure of living together in strained conditions may have led to fragile bonds forming. 

But, you win some and you lose some. Reflecting on GCS, it certainly wasn't all bad.  Again, some comments of mine from the early issues:

Dini and others were inhibited from exploring Harley's “obvious Jewishness” in the animated series to full potential, censors putting a nix on any mention of religious cultural identity, and it's an aspect of who she is that has never been addressed by other writers. Already Dini is bringing it further to the forefront and it's a welcome rounding out of something that has always been implied as part of her history – too often, comic book characters are denied any culture or religiosity excepting Christian (when they're good-aligned) and vaguely Muslim or Satanistic (when bad-aligned). 
Delightful to me is further exploration of her “little girl” identity. Again, something too risque to be anything much more than subtext in the kids-focused canons where she has most featured, Dini now seems to be steadily – if still very subtly – bringing it out more. Subtle is best; you don't need to clang people over the head with it – it's still pretty obvious, even in the kiddie-oriented material . It's really nice to see it being done in a genuine, unforced, uncreepy, uncontrived and unsexual way – as it should be. Sure, it can be intensely sexual and erotic, being a kink identity – but that's not the default and certainly not with Harley, who seems more to have, in her insanity, mentally regressed.
Harley's curious sense of honour has already come up, with her diving in to rescue 'Bruce Wayne' (a plastic-surgery altered Hush) as repayment for him approving her release from Arkham some months back – and this gives her the opportunity to show off her incredible fight skills as well. Never underestimate this bubble-headed bimbo – she'll hand you your kidneys!
She's even showing off her innate perceptiveness and psychological skills as well as glowing, joyous confidence!
Her debated relationship with Holly seems crossed off here – there's no doubt they're real friends, but in keeping with Harley's flighty yet needy nature, she went in search of other company when Holly left, rather than follow her. The only person she follows is her Mistah J! The rest of the time she alleiviates loneliness with whoever is most convenient – yet also in the place she wants to be. 
Finally – testament to her abiding relationship with the Joker is indeed paid. Although I cannot be truly happy until they have been properly reunited in a way that does them justice, getting these little reminders is lovely and a balm to my shipper soul. They have worked on a dual level as well – first of all to remind us that Joker will always be Harley's number one, that their love – and reunion – is inevitable (something the other characters take for granted as well) – as well as seving as a very pointed message that no matter how flighty, flaky, dippy and perky Harley may be, she is freaking nuts! She's in love with the Joker – and if you can go there, then you have to be crazy – and subsequently, not someone anyone would want to mess with, or take for granted! 
We've even had the very pointed message in issue two that Joker reciprocates Harley's feelings – something else other writers have long disregarded.

And at the end of the day, GCS was a series that took place while the Harley Quinn fandom was in the midst of a swell of new activity, asserting itself with its ideas and convictions about the character, illuminating the way the relationship bewteen creators and fans can unfold, aided by the Internet.  It certainly took place at an interesting time in comics history and will, despite its various failings and potentials, be remembered for giving us this: