In the parallel universe of Earth-53, the Wayne family take a shortcut through Crime Alley to return to their car after a screening of Zorro. A mugger tries to steal Martha’s pearl necklace and ends up shooting both parents, traumatizing their son, Bruce. He swears this will never happen again, dedicating his life and his family’s billions to improving up the Gotham police force.
Earth-64: Bruce replaces the Park Row municipal street sign with a vast flashing neon sign reading “They call this called CRIME ALLEY, you idiots, DON’T GO DOWN THERE.” Ironically, the intense illumination and epileptic strobing of the sign render the alley utterly crime free.
Earth-232: The Wayne Foundation revolutionizes the world by perfecting bio-mimetic nanotech materials, but goes bankrupt after flooding the market with synthetic pearls. Pearls become so common they’re used as a cheap building material. Crime Alley is forever cobblestoned and lustrous.
Earth-441: Demented filmmaker Bruce Wayne purchases and destroys all extant copies of every version of Zorro. He spends his fortune constantly re-filming and re-releasing reboots of the pulp swordsman, as praised for their repeated mastery of revolutionary new cinema techniques as they are criticized for always ruining the third act by having Zorro time-travel to the present to stab a gun-wielding mugger.
Earth-722: A traumatized Bruce Wayne realizes that there can be no street crime without streets. He excavates and floods all roadways to create a network of canals, renaming Gotham as “New Venice”. Most desperate and starving criminals cannot afford rebreathers, and the remaining thugs becoming much easier to spot on their motorized gondolas. These are swiftly defeated by the city’s new champion of justice, Aquaman.
Earth-2289: Master psychologist Bruce Wayne spots the key flaw in the Gotham criminal population. He becomes a Broadway producer, hiring every thug in the city to act as costumed chorus lines for the greatest musical stage show ever made. Without minions the Gotham criminal scene collapses. The show goes on tour, hiring all those drawn to strict-yet-ridiculous direction and uniformed clothing. Spin-off shows start in Metropolis and Central City, spreading to every country of the world. Every criminal organization loses its membership. The Joker dies when he can’t resist the urge to honk the horn while assembling his own dynamite-laced bumper cars.
Earth-15743: Bruce Wayne realizes that, holy shit, his parents were shot. He convinces Superman to take, like, five minutes to fly around the city destroying all illegal guns. Wayne Industries funds a global campaign to repeal the Second Amendment. The Joker becomes spokesman for the NRA. This is considered a step towards moderation and sanity by the organization, since it means replacing Wayne LaPierre.
For more Bat-madness, behold The Dark Knight’s Dumbest Moments (Come From His Best Bat-Qualities), or see him fight facehuggers in Prometheus Unbound: The 4 Craziest Alien Crossovers.