Given all the - traditional - vagueness associated with the Joker's origin, it should come as no surpise that the story of how he came to the pages of Batman's comics is also a muddled one. Apparently the product of three creators, Joker's true origin - whether it was down to Bob Kane, Bill Finger or Jerry Robinson or all three - died with those three.
But there is something interesting - and very pertinent - about Robinson's account of the Joker that has shaped the way the character has appeared in his various movie appearances over the years.
In the comics, Joker was initially a murderous force of nature and a typically unhinged serial killer type. The initial plan was to kill him off after his second appearance as his continued appearances was deemed to compromise Batman's ability as a hero. Thankfully, that was overruled and he returned to become Batman's most famous villain of all time.
From, there, what Robinson said about him rings particularly true. He claimed in 1975 that he wanted to create a supreme arch-villain who could really test Batman, and not just a run-of-the-mill crime lord designed to be disposed of after one story. Even more pertinently, he wanted to establish Joker as a reflection of his studies at Columbia University into characterisation on the importance of contradiction. Joker became Batman's contradiction.
Unfortunately, controversy would eventually clip Joker's wings through the second half of the 1950s as the Comics Code Authority stamped down on comics content and turned the increasingly murderous Joker into a goofy moron. At that point his clown appearance became less of an expression of the grotesque intended to shock and more a fitting costume or the fool he'd become.
By the time the first Batman movie came out, he was still that same fool, even as the comics had relegated him to the verge of obscurity, but there was still something important in his relationship with contradiction that still rung true...