Detective Comics
Detective Comics is an American comic book series published by DC Comics. The first volume, published from 1937 to 2011 (and later continued in 2016), is best known for introducing the superhero Batman in "Detective Comics" #27 (cover dated May 1939).
Joker (character)
The Joker debuted in "Batman" #1 (Spring 1940) as the eponymous character's first villain, shortly after Batman's debut in "Detective Comics" #27 (May 1939). The Joker initially appeared as a remorseless serial killer, modeled after a joker playing card with a mirthless grin, who killed his victims with "Joker venom": a toxin which left their faces smiling grotesquely. The character was intended to be killed in his second appearance in "Batman" #1, after being stabbed in the heart. Finger wanted the Joker to die because of his concern that recurring villains would make Batman appear inept, but was overruled by then-editor Whitney Ellsworth; a hastily drawn panel, indicating that the Joker was still alive, was added to the comic. The Joker went on to appear in nine of "Batman"s first twelve issues.