|Full Name||Gretchen Whistler|
|Occupation||Arkham Asylum Psychiatrist|
|Base of Operations||Arkham Asylum|
|Voice Actor||Adrienne Barbeau|
|First Appearance||Batman: Arkham Asylum (2009)|
Before Arkham Asylum Incident
When Quincy Sharp reopened Arkham Asylum, Gretchen started working there as doctor, and was committed to restoring her patient's sanity. One of her most noticeable patients was Killer Croc, whom she treated from the moment that he was sent to Arkham Asylum. Other patients of hers included the Riddler and Victor Zsasz.
Arkham Asylum Incident
Dr. Whistler was on duty when the Joker took over Arkham Island. She was locked in the Patient Pacification Chamber where Zsasz was keeping a guard named Mike hostage. After Zsasz was taken down, Batman left Gretchen with the guards in the room. It was unknown if Gretchen survived, but it was likely, as she was locked in a room with many armed security guards.
- Gretchen's known patients included: Killer Croc, Victor Zsasz (transferred from Dr. Sarah Cassidy), and the Riddler (transferred from Dr. Penelope Young)
- Gretchen's voice was also heard during Harley Quinn's first Interview Tape, although she was simply introducing Harley as an intern at the Asylum, before her indoctrination with the Joker.
- In the ArkhamCare website, Gretchen's surname was "Westler".
- The password to Westler's ArkhamCare file was "Horowitz"; her mother's maiden name.
- Gretchen stole Penelope Young's soy milk from the office fridge.
- Gretchen had a female dog named Nixon, who had separation anxiety, and a husband, Jason Whistler. The pair were going to Maui for Thanksgiving, and, as such, were looking for a kennel for Nixon, and opted to ask Dr. Kellerman where he kept his laborador, Murphy. He usually dropped him off at Cas di Rex in the Palisades, which cost $40 a night.
- Of all the Medical Staff at Arkham Asylum, Gretchen appeared to be the most understanding, patient, and fearless of them, seeing as how she apparently took no offense at Killer Croc calling her a "bitch" and showed no fear at Croc despite the fact that he made many references to killing and mutilating people and also threatened to kill her after his attack on Aaron Cash (as revealed in Croc's Patient Interview Tapes).
- Gretchen Whistler was German as she spoke with a thick German accent.
- It's unknown if Gretchen survived the Arkham Asylum Incident, but it is possible.