Christopher Nolan’s Dark Knight Rises, released in 2012, is considered the tenth greatest film of all time according to the Internet…
The creatives maintain that Gotham is set in no particular period. However, close observance of several aspects directs towards the fact that Gotham is set somewhere in the 1990s and the early 21st century as evidenced by flip phones, the mode of dress, the computers, and the retro sets.
The acid scene brought out the similarity between Harley and the Joker’s origins. As part of his origin story, the Joker fell into a vat of chemicals. It was what discolored his skin and colored his hair green, finally driving him insane. Later, it was implied that the chemicals also gave him some healing factor, as the Joker has survived injuries that should have left him dead on multiple occasions. He also seemed to be immune to most toxins and also once cut his face off, wore it as a mask, and then had it sewn back on with no ill effect.
The exact quote likely originated from the movie The Dark Knight, but it could have been inspired by some previous quotes and philosophies, for that matter. But because there are no exact references to or variations of this quote before the movie release, we can conclude that the quote is originally from the movie, The Dark Knight.