David Endocrine was a late night talk show host operating ten years after Batman retired. He has an assistant showman named Frank who announces from a podium at the side the new guest with a brief humorous description of them.
Shortly after Batman returned to crimefighting since his decades-long retirement, David Endocrine planned a new episode featuring the supposedly-reformed Joker after Dr. Bartholomew Wolper arranged to have him appear. The episode upon being announced was considered highly controversial. Upon announcing the Joker, and questioning him, the Joker managed to kill everyone, including Dr. Wolper and Endocrine himself, the former via a neck-snap and the latter with the laughing gas from two of Joker's robotic drones Bobby and Mary. Besides the Joker, Endocrine also had sex scientist Dr. Ruth appear on the show, although Joker killed her via kissing her.
In other media
David Endocrine appeared in the film Batman: The Dark Knight Returns Part 2 where he played the same role as in the comic. However, a difference is that he only had Joker and Dr. Wolper on the set, as Joker's killing Dr. Ruth was cut from the film. Additionally, Dr. Wolper's throat is slit by the Joker with a broken mug instead and Endocrine's death is shown on-screen, whereas his death in the comic occurred off-panel.
- David Endocrine is a parody of the late night talk show host David Letterman, and his physical appearance in the comic was modeled after him. In the film version, he was modeled after Conan O'Brien, his voice actor, who is also a late night talk show host.