This year, Gotham was sadly missing from the events of San Diego Comic-Con, since the Fox drama is just going into production this week on its fifth and final season, which is set to debut in 2019. Thankfully, though, Bruce Wane himself David Mazouz was on hand to offer a few clues about what we can expect to see as the show heads for its conclusion. The star confirms that Catwoman and Batman will both finally appear, and in speaking to how the GCPD's failures lead to Batman's arrival, Mazouz seems to hint at the legitimate emergence of The Joker himself. Or maybe not... In his words:
Bruce is going to have that realization this year, he's going to have that moment, and he's gonna also show down with some of the villains that we know. Some of the big names. And one of those names might start with a 'J.'
Let's take a step back here, just to look at everything from a big-picture perspective. Gotham has been inching its way down the Joker trail ever since Season 1, when Cameron Monaghan was first introduced as Jerome Valeska. After resurrections and facial reconstruction and more, Jerome was killed off and replaced by his far more pathological brother Jeremiah, who lacks his sibling's high-pitched cackles. But we already knew that Jeremiah and Bruce weren't on good terms with each other in the end, so it wouldn't be much of a tease to say that they'll butt heads again. But since Gotham's producers have stated the Valeska brothers would be highly influential to the Clown Prince of Crime in this version of Gotham City, perhaps Jeremiah's reign of terror will come to a pasty-faced conclusion in the wildest way possible.
With the various Joker projects in development for the big screen, Gotham's lack of a proper Joker has been partially fueled by DC and Warner Bros. not wanting to use the character across multiple platforms, similar to how Arrow wasn't able to use Harley Quinn when the Suicide Squad movie was going into development. So it's possible that Gotham still isn't able to use the name "Joker" to refer to its maniacal villain, which is where the Mr. J moniker would get play.
Unfortunately, David Mazouz didn't elaborate to TVLine what the "J" stands for, so it could technically stand for Judson Caspian, a brutal vigilante baddie who targets and murders juvenile delinquents. Or maybe it'll be Jason Todd, although that explanation would take way more story alterations than the ones done with Jerome and Jeremiah.