In many respects, Joker hearkens all the way back to the 1928 silent The Man Who Laughs , which inspired the comics character in the first place.
Nevertheless, just as the original Joker character was visually inspired by Paul Leni’s 1928 film, The Man Who Laughs, the new Joker draws its dark inspiration from all Batman-themed films and comics that precede it, especially Alan Moore’s 1988 graphic novel, The Killing Joke, which imagined the Joker's origins as a comedian.
Debuting in Batman’s first adventure in 1940—his appearance is said to have been based on Conrad Veidt in 1928’s The Man Who Laughs —the character helped to popularize the “sinister clown” archetype that ultimately led to Pennywise.