Five small-time criminals served under the Joker in the robbery of Gotham National Bank,& four of which were methodically or accidentally killed off in the heist. The Joker himself posed as one of his thugs, going by the call-sign Bozo. Going by one of the people involved, Grumpy's response about splitting it up into six shares instead of five, the heist was not the first time where the Joker disguised himself as one of his own thugs when they participated in a crime of some sort.