"Call him what you will -- the Clown Prince of Crime, the Harlequin of Hate, the Ace of Knaves, or even 'Mr. J' -- but Batman's arch-foe the Joker is one of the most recognizable of all supervillains. His chalk-white skin, green hair, rouge-red lips, and toothy, macabre smile are etched into infamy, evoking the clown fears that have traumatized countless children and have lingered in the nightmares of many adults."
* Wallace 2014 p40
"The Clown Prince of Crime. The Harlequin of Hate. These titles try to capture the Joker's innate contradiction as a showman gone sour, but the character is far too chaotic to be summed up by a label. As one of the biggest figures in popular culture, the Joker is in the unique position of being more popular than many DC Comics heroes. As Chuck Dixon, writer on the Batman titles during the 1990s, puts it, 'Joker stories are not about Batman. They're about the Joker."
* Wallace 2014 p40-42
"Unique interpretations of the Joker by writers, artists, and actors all share a common core of madness. 'The Joker reinvents himself every morning,' explains Dixon. 'He's whatever you need him to be. He presents an intellectual, psychological, and physical challenge for Batman. He's the whole package.'
"Jim Lee sees brilliance in the Joker's design. 'He's this thin, wiry, very over-the-top caricature of the creepy clown from people's nightmares,' he says. 'That contrasts well with the shorter, blocky, shadowy silhouette of Batman. And his whites, reds, and greens really pop against Batman's grays and dark blues.'"