"...You can address me as Mr. J."
"It's amazing what people believe...just because it's on the Internet."
Dr. Harleen Kopski née Quinzel
"Dr. Quinzel, overseeing Patient #4479."
- Big Damn Heroes: "Matches Malone" is a geriatric man already written off as suffering from dementia before getting a knife to the back. Later, he staggers down the hall toward three Arkham inmates... whom he casually defeats in moments before The Reveal that Matches is Batman in disguise.
- Chekhov's Gunman: Got a few offhand mentions and was the subject of an April Fools joke before appearing in person in Episode 17.
- The Dreaded: Joker has a very noticeable Oh, Crap! reaction when he shows up at the church.
- The Ghost: Was only mentioned most of the time in Season 1. Makes a physical appearence in Episode 17.
- Lights Off, Somebody Dies: The second part of his entrance in the church.
- Mythology Gag: Season 2 drops Matches Malone's name early on. Fans of the comics know exactly what to expect.
- Stealth Hi/Bye: Does the "Bye" part at the end of Episode 17, after getting shot no less, does the "Hi" part in The Stinger to Episode 19, both occasions doing it to the Joker.
- Super Window Jump: The first part of his entrance in the church, if the offscreen sounds of shattering glass are to be believed.
- Walking Spoiler: Notice anything here?
Dr. Jeremiah Arkham
- Anti-Villain: His main motive above all else is to save his comatose wife.
- Big Bad: Shaping up to be this for Series Two.
- Beard of Sorrow: Appears to be growing one of these.
- Composite Character: The storyline involving his wife is similar to that of Mr. Freeze and Nora.
- Deadpan Snarker: Even in the face of death and danger, he's perfectly willing to match wits with Joker.
- Distressed Dude
- FaceHeel Turn
- From Nobody to Nightmare
- He Who Fights Monsters: In Season 2, to the point of recruiting Scarecrow to work for him by promising his old job and office back in return.
- Trauma Conga Line: First, Arkham is carjacked by the Joker and forced to act as an accomplice to his kidnapping of Bolton. Then he is taken to his house, tied up along with his wife, and told that a bomb will kill her at midnight unless he follows his instructions. Then, after the church incident, he escapes in the middle of shootout between the Joker and Gotham police, only to be captured again after the Joker commandeers a squad car. Then, after being forced to sell the asylum to Lex Luthor, he watches as his house blows up with his wife still inside it. She survives, but is in a vegetative state with little chance of recovery. That in a nutshell is what amounts to his Start of Darkness.
- Woobie, Destroyer of Worlds: His repeated traumas and humiliations at the hands of the Joker (sometimes played for Black Comedy) leads to him becoming one of the main villains of Season 2.
Dr. Jonathan Crane
- Bald of Evil: Although not as evil as usual.
- Pet the Dog: While he does it for selfish reasons, he tries to convince Harvey to come back to the light.
- Pragmatic Villainy: Ultimately considers acquiring Arkham Asylum more trouble than it's worth, and agrees to sign it back over to Dr. Arkham. However, Arkham thinks this is merely Lex Luthor Code for "As soon as I get out of here I'm paying a hitman to shoot you in the face", so he has Two-Face shoot Lex instead.
- Unexpected Character
- You Look Familiar: Same actor as Hugo Strange.
Dr. Hugo Strange
- "Awesome McCool" Name: Lampshaded. Joker doesn't think that's his real name at first.
- Berserk Button: He loses it when Joker implies he's met his wife in some way... at his house no less.
- Start of Darkness: Dr. Strange has left Arkham and plans to start his own clinic, with a special interest in the psychology of the Batman...
- What the Hell Is That Accent?: According to the actor, it started off a Germanic accent, then it mutated into some sort of Jamaican accent while filming.
Ted the Bum
- Better Living Through Evil: He says he's cooperating with the Joker because he wants to die, but you can tell the respect is a factor.
- Canon Foreigner: Appears to be a completely original character rather than an existing Batman or DCU personality.
- Death Seeker: As a result of his life being ruined by a number of events, he's perfectly fine with dying. It's because of this that the Joker takes a liking to him.
- New Job as the Plot Demands: His claiming to have held wildly varying jobs is a Running Gag. It's unclear whether he's lying to try and make himself sound useful or whether he's actually a big enough screw-up to have had and been fired from all of those jobs. It's confirmed that he was at least telling the truth about being a GCN cameraman. He was married to Summer Gleeson while he was employed there.
- Not-So-Harmless Villain: Well, more of an Anti-Villain, but Ted is still far more competent than he appears. Case in point, in the second season, he helps the Joker escape by covertly passing off a metal spoon to him so that he can cut his bonds. Bonus points for doing it as a magic trick. Judging by the smile Joker gives him, he was pretty impressed. He's also pretty hand with a gun.
- Punny Name: His full name is apparently Theodore Bayer. Say it out loud.
- Of course he does work for the Joker. It could be an alias with the pun being intentional.
- Wild Hair: In Season 2 he has long hair and an unkempt beard, making him look much more like a homeless bum than in Season 1.
Dr. Thomas Elliot
- Bi the Way: Beds every guy he puts his eyes on, and Selina Kyle. He also leaves a message on Bruce Wayne's answering machine about Andrea Beaumont, who both he and Bruce apparently have a thing for.
- The Casanova: Is apparently able to charm men into bed in extremely short order, usually starting with just a smile. Although, since they are men, this may have more to do with certain other tropes than it does with this one.
- Mythology Gag: "I like to keep my involvement with the Wayne family Hush, Hush."
- He also threatens to rip Selena's heart out.