The Joker (Telltale)

"John Doe" is a patient at Arkham Asylum. No one knows about who he is and what he is doing at the Asylum, including the staff themselves. He would be later known as "The Joker" after the events of "The Children of Arkham"

Biography
Though it is obvious this so called "John Doe" is the Joker, nobody truly has an identity for him. His background is unknown, not giving much of a story to anyone who meets him. Though he doesn't get out of Arkham, he knows that Vicki Vale is Lady Arkham, and that he suspects that Bruce has something darker within him, hinting that he may know Bruce and Batman are one person. He may have just been referring to how he attacked Oswald, simply guessing that Bruce wanted more than to just hurt Oswald, even though Doe knew Bruce was drugged at the time.

Episode 4: Guardian of Gotham
Within the game, he has helped Bruce Wayne twice, once during an attack against him in Bruce's own cell, and creating a distraction so Bruce can reach a phone to either call his lawyers or Gordon to help get him out. He is last seen walking away from Bruce, laughing maniacally.

Episode 5: City of Light
John Doe isn't seen much in the fifth episode, but is seen when Lady Arkham frees the inmates from Arkham Asylum. He seems to stand alongside Batman as he watches the Chaos ensue, enjoying it thoroughly, even going so far as to simply calmly watch as the inmates run amok, drinking what seems to be water as he does so. He is seen at the end of the episode with his trademark red lips, and finally has his formal Introduction as "The Joker"

Character
"John" seems to be a rather sadistic character, enjoying the pain of others, for the thrill of entertainment. Such example is when he caused Zsasz to have a violent outburst, due to his tallymarks not being equal to his kill count, saying he "hasn't had this much fun in a long time." He also seems to enjoy chaos in general, as he seems to find the Children of Arkham's actions fairly entertaining, and Harvey's wavering sanity is painfully obvious to him, but he enjoys it. He also seems to enjoy harmless pranks, giving Bruce Wayne a key that didn't seem to unlock anything, laughing at how Bruce "actually tried it."

Bruce Wayne
John was very welcoming to Bruce when he first arrived, personally saving the billionaire from a group of patients that tried to attack him. He even willingly organized him to give him a chance of making a phone call. Dialogue he shares with Bruce hints that he may know the billionaire is actually Batman.