The Joker, DC Comics' quintessential agent of chaos and Batman's arch-nemesis, first appeared in Batman #1 (spring 1940, published April 25, 1940), created by Bill Finger, Bob Kane, and Jerry Robinson. Debuting as a homicidal criminal mastermind with pale skin, green hair, and a grotesque grin, he used Joker venom to kill victims while leaving them with rictus smiles, establishing him as a lethal psychopath in his initial stories. A key early development came in Detective Comics #168 (February 1951), where Finger introduced the influential origin of the Joker as a failed criminal known as the Red Hood who fell into a chemical vat during a heist, emerging disfigured and insane—this "one bad day" concept has shaped subsequent interpretations, though the Joker frequently claims multiple, conflicting backstories to underscore his unreliability.
Influenced by the Comics Code Authority in the mid-1950s, the Joker was reimagined as a harmless, prankster thief during the Silver Age, toning down his violence to align with child-friendly standards. The Bronze and Modern Ages restored his menacing lethality, notably through Denny O'Neil and Neal Adams' 1973 story "The Joker's Five-Way Revenge" in Batman #251, and landmark tales like Alan Moore and Brian Bolland's The Killing Joke (1988), which paralyzed Barbara Gordon and explored madness as a response to tragedy, and "A Death in the Family" (1988–1989), where readers voted for him to murder Jason Todd.
In recent developments, stories such as Chip Zdarsky's "The Joker: Year One" (2024 in Batman #142–144) delved into his early psyche with multiple personality elements inspired by Batman: Three Jokers (2020), while the Absolute Universe introduced a monstrous, horror-infused variant in Absolute Batman (2025). Remaining an embodiment of anarchy with no fixed origin, the Joker continues to evolve as a psychological terror and cultural icon in ongoing series and crossovers.