Its official, "Batman: The Killing Joke" is now part of the official storyline of the DC universe, as the graphic novel has been incorporated as a key story for the continuity of their Rebirth scheme for the whole franchise.

The said 1988 graphic novel by Alan Moore has been chosen and established by the ongoing "Doomsday Clock," which melds together the Watchmen and the Justice League. This much was confirmed in the second issue of "Doomsday Clock" released on Wednesday, Dec. 27, where some eagle-eyed fans spotted a familiar setting.

In the second issue, Nite Owl with Ozymandias and company commandeered the Owlship to a different dimension where Doctor Manhattan might have travelled. The group is now seeking him in order to bring peace back to their world, which is on the brink of chaos due to Ozymandias' actions. The Owlship landed on a derelict amusement park with dilapidated rides, which fans of "The Killing Joke" have unmistakenly remembered as the place in the said 1988 graphic novel where the Joker took residence.

This was also where the Crown Prince of Crime kidnapped and tortured Commissioner Jim Gordon in an effort to turn him insane and draw the attention of Batman in the process. It is worth noting that the Owlship also crashed into none other than Gotham City, Bruce Wayne a.k.a. Batman's hometown and domain, meaning the first run-in of the Watchmen may be with the Dark Knight himself.

Comic Book has suggested that while the amusement park may just be a homage to Moore's work since he also authored the original "Watchmen" series, the structural similarities of it to the one in "The Killing Joke" is too uncanny to be passed off as just a simple nod or reference. This poses a lot of other possibilities for the future of "Doomsday Clock" and the rest of the DC Rebirth plan, where Barbara Gordon is already a cripple because of the Joker.

If this was the case, then hardcore fans of "The Killing Joke" should also be aware that the future issues of "Doomsday Clock" may finally address what Batman really did to the Joker at the end of the 1988 graphic novel. Whether he killed him or just shared a moment of madness with him before incarcerating him again might get answered soon.