In the patient interview tapes for Harley Quinn, much of the dialogue is taken directly from the Paul Dini/Bruce Timm one-shot comic 'Mad Love', which was later adapted into an episode of "The New Batman Adventures" (1997), also by Paul Dini, writer of Arkham Asylum.
The Game's version of Arkham Asylum is heavily influenced by the version that existed in the comic books, as it features strong elements from the stories of Alan Grant, the limited series "Arkham Asylum: Hell on Earth" and very obvious references to Grant Morrison's graphic novel: "Arkham Asylum: A serious house on a serious earth", among other influences.
The game is very faithful to the comics and uses Batman's rich history and decades of DC comics mythology as a narrative guide, visual reference and the opportunity to explore more of the darker complex themes each of the villains embodies.
Killer Croc originally started out as a man born with a unique skin disease that gave him scaly skin and very reptilian-like attributes. The version of the character in this video-game reflects his appearances in the comic books after the year 2000, where he actually mutates into a rather large crocodile.
Even though this is an open world "sandbox"- type game, limited to Arkham island, at no point does Batman take a rest from his detective work. The game saves every time the player enters a new area on the island.
The trivia items below may give away important plot points.
This game features the second largest collection of villains appearing in a Batman Video game including cameos, after the verifications made by it's sequel, Batman: Arkham City (2011) (as of September 2011). Those who make appearances are The Joker, Harley Quinn, The Riddler (although he is only heard and not seen beyond the character biography artwork), Killer Croc, The Scarecrow, Bane, Poison Ivy, Victor Zsasz, the dummy known as Scarface (albeit without the assistance of the ventriloquist Arnold Wesker) and Clayface (who is also not seen in his true form but in the guise of multiple characters in a cell in the penitentiary).
There is a hidden room in the Arkham mansion, where after applying three sprays of the explosive gel on a wall, players can enter and see blue prints, pictures and plans for the sequel, Batman: Arkham City (2011).
The twist behind the Joker's scheme to fight Batman by using the titan formula is strikingly similar to an episode The Batman: Brawn (2005), where he combats him after getting hold of Bane's venom formula.