On “Seinfeld,” George Costanza’s secret ATM code is Bosco. He refuses to reveal it even when the situation becomes so extreme that his mother is lying on her deathbed.
The gag comes from “The Secret Code,” the seventh episode of season seven, first broadcast on November 9, 1995. George treats his ATM passcode as inviolable, telling Jerry that he would disclose it only to save someone’s life—but he cannot imagine a realistic situation that would qualify.
That situation eventually arrives. While visiting his mother at the hospital, George confides the code to her because he wants the secret to die with her. She repeats “Bosco” as her final words, unintentionally exposing it to J. Peterman and others.
The code’s absurdity is part of the joke: “Bosco” is also the name of a chocolate syrup brand, and Kramer later tries to deduce George’s code by considering which syrup he likes. George ultimately loses the secret when the code is needed during an emergency.