As soon as you say "Batman," most people will either say back "Robin" or "The Joker." Batman and The Joker are two sides of the same coin, after all, with one's psychosis driving them towards order and the elimination of crime, and the other's pushing toward chaos and the propagation of crime. It's natural, then, that when Gotham was revealed, promising the origin story of the city itself, and eventually of Batman, many fans instantly wanted to know when the origin of The Joker would be tackled.
Bruno Heller, the showrunner, and other writers and producers have continued to throw fuel on that fire. Early promises were to tease The Joker many times before finally revealing the villain. A stand-up in Fish Mooney's nightclub was the first. Then we had Cameron Monaghan and his laughing, murderous carnie. The Red Hood gang came next, and the riot at Arkham with a bloody-lipped victim and a laugh in the background made some people wonder. And that's all part of the plan.
Heller, in the past, has said "we will scratch the surface" of the Joker's story. He then said specifically of Monaghan's character Jerome, "He may or may not be The Joker. It's a long game we're playing here." His biggest hint, however, may have been one of his earliest. Right after that comedian appeared, Heller said, "The Joker didn't think of his shtick all by himself. There must have been someone before who The Joker saw and thought, 'Oh, that's a good shtick. I could work with that and make it better.'"
Finally, at Comic-Con International: San Diego this past July, this little gem from Heller and fellow EP Danny Cannon came out when they were talking about Jerome.
"We got a little bit of a tease of the Joker last season, so what's his presence going to be like this season?
Cannon: Well, he's in Arkham—if that is in fact the Joker. He's in Arkham, and Barbara Kean is put in the same wing as his in Arkham, which is for the worst of the worst. And an event happens, which allows him be involved the next few episodes.
Heller: He gets to fulfill his destiny in a very grand way."
Put those last two parts together and what do you get? The first real hint that Gotham could do something crazy (and crazy awesome): make Barbara Kean into that world's Joker.
We know already that the world of Gotham is different from any other DC Universe we've seen before. Thanks to the history of the multiverse - different versions of the universe where sometimes things are only slightly askew and sometimes they're drastically changed - we've been familiar with the concept at DC Comics that these characters and concepts fit into their own worlds in unique ways. Gotham, for instance, has an Edward Nygma that works at the GCPD. It has a young Selina Kyle, Bruce Wayne, and renamed "Ivy" that are all friends - or at least have been friendly. In other words, nothing about Gotham has to go the same way that it ever has in the comics that inspired it, and that's what makes the show exciting.
It's also what would allow them to go in a very different direction for The Joker. In the Flashpoint universe, it was Bruce who was murdered, instead of his parents, with his father becoming Batman and his mother becoming Joker. Likewise, in modern Batman comics, Barbara and James Gordon's son became quite the tortured killer himself. That slight inspiration could be used for the new Joker here. In the final episodes of season one of Gotham, it's safe to say Barbara Kean lost it. Already a bit disturbed after years of abuse from her parents, Kean's time with The Ogre broke something; it's worse than your garden variety Stockholm Syndrome, too, though she does seem to think she loved him somehow - she also says it was she that killed her parents, not the serial killer. After this, she followed up with an attack on Lee Thompkins, and we know that finally landed her in Arkham Asylum, where she'll be at the start of the season.
Of course, if everyone who stabbed someone was a candidate for the Joker on Gotham, then our list would be about 30 people long. The moments that make Barbara the prime suspect are subtle, and could really be beautiful filmmaking if it plays out this way. It's all about Barbara's slight, small grin. The first time this terrifying smile hits her lips is when Ogre shows her his torture room. It flashes again, twice, when she tells the story of her parents to Lee. It's this little grin that could be the major moment of foreshadowing everyone has been looking for, but isn't looking in the right direction.
The other clue comes with the fact that she and Jerome share a general living space at Arkham Asylum, which brings us back to that quote: "The Joker didn't think of his shtick all by himself. There must have been someone before who The Joker saw and thought, 'Oh, that's a good shtick. I could work with that and make it better.'" With the pair finding themselves in the same place, Jerome could be the next stepping stone on Barbara's path to laughter and terrorism.
So will Barbara Kean, instead of becoming the wife of Jim Gordon, become the worst enemy Gotham City has ever seen? We'll just have to watch Season 2 of Gotham - surreptitiously subtitled "The Rise of the Villains" - to find out.
Slight Disclaimer: Since first postulating this idea and writing the original draft, I've also seen the first three episodes of Gotham season 2. I will give no spoilers here, and am leaving those episodes - with support or denial of my theory - completely out of this piece. More once they have aired!
Gotham Season 2 begins September 21, 2015 on Fox.