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.

Number of times Batman has been knocked out: 7.

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.

Planned for release in the US on the same day as Batman: Year One (2011).

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.

The first open-world Batman video-game.

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.

After finding Deadshot's weapon cache, if you look downward, you will find the hilt of a lightsabre. Mark Hamill, who voiced the Joker, portrayed Luke SkyWalker in the Star Wars films and his weapon was a lightsabre.

After the release of this game, Mark Hamill announced he was retiring from voicing the Joker. However, he said that if an adaption of the graphic novel "Batman: The Killing Joke" was ever released, he would return to the role. Batman: Arkham Knight featured a flashback to this event, and Hamill returned as The Joker for it.

In the expansion pack of this game called "Harley's Revenge" it is revealed that the hint of her being pregnant in the main story was either a false positive or she lost the baby through miscarriage.

Before you realize there is a fake Joker, you can hear Harley Quinn say something along the lines of "Oh Mistah J you look perfect! Oh wait it isn't you is it?" And Joker says "Be quiet Harley!" This is a foreshadowing hint that Clayface impersonates Joker later on.

Find either a balcony or a bill board and spam freeze grenades. You will start to float in the air. If you go high enough the TYGER guards guarding the wall on the edge of arkham city will not spot you and you are free to roam gotham city.

During the Joker boss fight that takes place a few minutes before Protocol 10, if you switch to detective mode while fighting him, you can see that he doesn't have a skeleton while the thugs and lieutenant do. This is one of the many hints given throughout the main storyline that Joker is just being imitated by Basil Karlo/Clayface.

In the end of the third Catwoman DLC mission, the player is presented with a choice: Leave Arkham City with her loot, or leave it behind in the vault, but save Batman who has become trapped in the Steel Mill. On the floor, a green arrow points towards where the "better" option of the two is (save Batman), and likewise for the red arrow pointing towards the "lesser" choice (leave Arkham City).

At the beginning of the game when you are told to get in line an inmate says "Bruce Wayne. You're on my list. Bang!" This is Deadshot out of costume. Later in the game you track a sniper assassin throughout Arkham City and find out it is Deadshot and he has "a list of targets." One of which is Bruce Wayne.

In the scene towards the end of the game when you are in the monarch theater before you fight clayface, the film that has ended is "The Terror", which in clayface's storyline in the comics was the film he was most famous for starring in.

It is implied by one of Harley's goons in the "Harley's Revenge" DLC that The Joker is still alive after dying from the titan formula.

Right before you first encounter the Joker, near the steel mill on top of a nearby building you can find scarecrow's mask on a pile of straw. Showing he was not killed by Killer Croc. This foreshadows his return in _Batman: Arkham knight (2015) (VG)_ ( qv).

While "Joker" explains his favourite TV show telling everyone he is all better now you hear someone cough behind the camera that's is one of the many signs that Basil Karlo/Clayface is imitating The Joker