Part of the fun with the Joker is the ambiguity of his true identity. Sometimes he was Jack Napier, sometimes Joe Kerr (goodness gracious), sometimes a mafioso, or a comedian, or a heist man, etc. The multiple choices for Jokers past self increase when you take in alternate reality stories like Knight of Vengeance, which contains maybe the most dramatic recasting of his identity yet. In a reality where the Wayne family was mugged but only young Bruce was killed, Thomas and Martha Wayne were destroyed by their grief. As their marriage splintered, Thomas tracked down and murdered the mugger and became Batman. Martha carved a permanent smile in her face and became the Joker. The plot kicks off as Joker kidnaps two kids and holds them at Wayne Manor. There, Batman and Joker, husband and wife, have their brutal final showdown.
