After much research, Nolan's brother and co-writer, Jonathan Nolan, suggested the Joker's first two appearances, published in the first issue of Batman (1940), as the crucial influences.
Nakon mnogo istraživanja, Nolanov brat i suscenarist, Jonathan, predložio je Jokerova prva dva pojavljivanja u prvom izdanju Batmana (1940.), kao ključne utjecaje.