Martin Jarvis, Nolan North, Chris Cox, Peter MacNicol, Tom Kane, and Grey DeLisle reprise their respective roles as Alfred, Penguin, Deadshot, Mad Hatter, Quincy Sharp, and Vicki Vale from Batman: Arkham City. Likewise, Wally Wingert reprises the role of Edward Nymga/Nashton, albeit under the pre-Riddler alias Enigma and Tara Strong returns as a pre-Harley Quinn Harleen Quinzel. "Cold, Cold Heart" also sees Maurice LaMarche return as Mr. Freeze and in the game proper, he's Cyrus Pinkney.
Lying Creator: Before the game's release, the "Worst Nightmare" skin was stated to be available in the main game and vaguely implied to be unlocked with 100% completion. However, those who managed to achieve that feat never unlocked it for use, causing much speculation on how it was to be obtained. Complicating the problem, the developers kept quiet for some time, before eventually admitting that it had been "removed" in testing, and was never in the commercially released version.
Name's the Same: Michael Gough, voice of Jim Gordon is not to be confused with the late Michael Gough who played Alfred in the Burton/Schumacher Batman films.
Prop Recycling: A particularly strange instance, as Mark Hamill's loudspeaker cackles from City are recycled for some of the multiplayer maps.
Likewise, gun racks in the GCPD still bear the familiar Arkham logo, despite the facility being closed at the time of the game.
A photo of Arkham guard Aaron Cash's family can be found in a locker at the police precinct - the same one from City, meaning that it includes not only two young children who were likely not born yet at this point in the series' continuity, but an infant who was only born after the events of Asylum.
One of the freeze gadgets from City appears in Cold, Cold, Heart as an item on Victor's desk in Gothcorp.
JB Blanc replaces Fred Tatasciore as Bane, which is surprising considering Tatasciore returns to provide voices in the game.
Brian Bloom replaces Nolan North as Black Mask. This one, like David Kaye taking over as Commissioner Gordon and Grey DeLisle as Martha Wayne in Arkham City, is puzzling, considering North is returning to reprise the role of Penguin, just as Tom Kane and Tasia Valenza (Gordon and Martha's respective voice actors in Arkham Asylum) reprised the respective roles of Quincy Sharp and Poison Ivy in City.
Michael Gough replaces Tom Kane and David Kaye as Jim Gordon; ironically, despite voicing a younger Gordon, Gough is older than both Kane and Kaye.
Khary Payton replaces Steve Blum as Killer Croc, despite Blum returning to voice Loose Lips and the Electrocutioner.