The Joker's Robbery of Gotham National Bank was Joker's first major attack on Gotham.
A textbook "take-over" robbery, the Joker's plan called for three masked thugs (including himself with the alias of "Bozo") to enter the lobby of the Gotham National Bank and subdue the employees, security guards, and clients, while two others swung onto the roof from an adjacent office building, one to disable the silent alarm before it could be tripped, and another to open the vault. Owing to their affiliation to the Joker, they each wore robber masks stylized in a similar manner to clowns. Unknown to any of the thugs, the Joker had also arranged a sequence of double-crosses, that would end with him being the only one left alive at the same moment the robbery was completed. He also secretly called in a bus driver to act as the escape vehicle.
While on their way to the bank, after picking up "Bozo," Grumpy and Chuckles conversed about the planned robbery: specifically, they will split the money amongst themselves, dividing it into five shares. Chuckles then corrects Grumpy that it would actually be six shares due to the fact that they naturally have to include the Joker, the one who planned the job. Grumpy then accosted him, implying that he intends to make off with the money without giving Joker his cut due to feeling he doesn't deserve a share for "sitting out," and also citing that he knows why they call him the Joker. Happy and Dopey arrived on the roof, also conversing with each other about why their boss was called "the Joker," speculating that it had to do with his wearing clown-like make-up to scare people in a manner comparable to war paint. Dopey, after disabling the alarm, was shot in the back by Happy, who made his way to the vault. Just before his death, however, Dopey noticed an oddity: Specifically, that the silent alarm was not going out to 9-1-1, but instead trying to reach a private number, although he dismissed it as not being a problem when asked by Happy. Happy then reached the bank vault and set up a device to bore open a hole to access the locks. However, while drilling, he ends up hit with a jolt of electricity, temporarily stunning him, causing him to realize that the vault was wired with at least 5,000 volts.
The Joker, Grumpy, and Chuckles stormed into the bank lobby to pacify those within, with Grumpy tackling a security guard and eventually pistol-whipping him on the back. This included an ingenious touch by which the Joker placed grenades into the terrified customers' hands and pulled the pins, ensuring that they could do nothing with their hands except hold on. In a surprise move Chuckles was killed when the Bank Manager opened fire with a shotgun. Grumpy was wounded after being tricked by the Joker into believing that he used his last round, while the Joker shot the manager in the legs. However, the wound was not fatal, with Grumpy yelling at his partner and accosting him, demanding to know where "[Bozo] learned how to count" before taking his leave. Grumpy then went to the vault, which Happy had opened despite the hidden electric security system by using his shoes as makeshift electric gloves, with Grumpy deducing from Happy's report on the electric system in the vault as well as their earlier encounter with the manager that the place they were robbing was actually a mob bank, commenting that the Joker was indeed as crazy as his reputation stated. Grumpy then shot Happy as ordered, although not before learning that Happy had killed Dopey under similar orders, with Happy also expressing shock and horror when learning what was to become of him, and loaded several duffel bags with the cash inside, also commenting that had the Joker been smart, he would have made sure they brought a bigger car to load the money inside.
Believing that he had been set up, Grumpy pointed his gun at Bozo just as he was about to retrieve the last bag, but was run over by a school bus driven through a wall, also expressing confusion when Bozo revealed that he intended to kill the Bus driver. The Joker and the bus driver loaded the cash into the bus, then Joker calmly shot the driver as he was questioning where the rest of the robbers were, and began to leave after retrieving the last bag. Just before he could leave, though, the manager, having witnessed the robber's earlier actions, told him with clear disgust for his actions that he'll just get rubbed out himself in the future and commented that criminals used to have honor and respect and then demanded what the robber believes in. The Joker couldn't resist showing his face to the manager and the security cameras, also sticking a grenade with its pin attached to its string while revealing that his belief is that "whatever doesn't kill you simply makes you stranger." The Joker then drove the bus away, pulling the grenade while driving off due to making sure the string was caught to the door beforehand, with it revealed to be a gas grenade releasing an unknown set of fumes. merging smoothly into a line of other school buses, just as the Gotham City Police Department started arriving from the opposite direction. As a result of the heist, the Joker stole upwards of $68,000,000