An Easter egg/reference relating to The Scarecrow can be found on a barge in the docks area. When on the barge, use the sequencer gadget to solve the code "City of Terror". A panel opens. Once inside, you are in a room filled with neon bug zappers. At the end of the hall, there is an unconscious inmate sitting in a chair. Upon zooming in on him, he is startled awake and gives a loud shriek. He goes back to sleep. It is assumed that he is a victim of The Scarecrow's experiments.
It is heavily implied at one point in the game that Harley Quinn is or was pregnant. This is suggested by examining Harley's costume on a dummy and panning down to the floor. At the dummy's feet is a box reading "Fruitful Endeavors pregnancy test". Lying beside it is a positive test.
When you go to Two Face's courthouse and you enter the back way; you can go down to the cell next to the Calendar Man's cell. When you're in that cell turn on detective mode, look up (make sure you are under them), and punch. When you do that they somehow notice you and run through the door and come to fight you.
There are several references to Lost (2004), the ABC television show. One when flying around Arkham City, an inmate asks another, "So, did they ever explain what the island was?" And later, more dialogue: "...why did it end in a church?" Writer Paul Dini was part of the "Lost" writing staff for the first two seasons before leaving the series.
This is the first known project where Tara Strong has voiced the role of Harley Quinn, which has predominantly been voiced by creator Paul Dini's friend Arleen Sorkin. Strong is better known in the Batman animated universe in the role of Barbara Gordon, aka Batgirl and in this game aka Oracle.
The code word "Sarah" given to the undercover officers by Commissioner Gordon is in reference to his wife Sarah Essen-Gordon who was shot to death by the Joker in Detective Comics #741.
During the Catwoman DLC mission to get her loot back from Two-Face, Two-Face says, "Whoever kills the Cat gets to be my number one... guy" in a manner very similar way to how Jack Nicholson's Joker says to Bob (the goon) "And remember... you... are my number one... guy" in the Tim Burton's Batman (1989) movie.
Troy Baker, who plays Tim Drake/Robin, plays Bruce Wayne/Batman in such games as Lego Batman 3: Beyond Gotham (2014) as well as Batman: The Telltale Series (2016) and Batman: The Enemy Within (2017).
While playing the Iceberg Lounge VIP Room Challenge Map DLC, Killer Croc can be seen drinking liquor and smoking a cigar while watching you fight in the background.
Rocksteady decided not to use the Batmobile in this game due to Arkham City's rugged terrain and narrow environments.
Of the four Batman: Arkhamverse games, this is the only one in which Commissioner James Gordon doesn't have a voice-over at the end, and also the only one in which he doesn't get captured.
Peter MacNicol voices The Madhatter - a villain obsessed with collecting Batman's cowl. MacNicol also voices X The Eliminator - a villain similarly obsessed with collecting part of the hero's outfit (his crest) - In Harvey Birdman, Attorney at Law (2000).
Rereleased in a remastered version for PS4 and Xbox One in 2016, together with its prequel 'Batman: Arkham Asylum (2009)' titled 'Batman: Return to Arkham (2016)'.
In the DLC, " "Harley's Revenge", you play as as both Robin (Tim Drake) and Batman.
Batman: Arkham City was "remastered" for the Xbox One and PlayStation 4 as part of the Batman: Return to Arkham (2016) Collection. When the remaster was initially revealed on May 18th, 2016, there was so much outrage about the very apparent graphical downgrades and stylistic changes that the remaster's release date was pushed from July 26th, 2016, to October 21st, 2016, in order to address the issues. The final product indeed ended up looking better than the reveal trailer footage, but many of the stylic changes remained, much to fan dismay.
The in-game super prison "Arkham City" bears a strong resemblance to the prison in John Carpenter's Escape from New York (1981), where Manhattan island has been walled up to act as a giant penitentiary.