Slavoj Žižek and the chicken joke from The Parallax View (2005):

“For decades, a classic joke has been circulating among Lacanians to exemplify the key role of the Other’s knowledge: a man who believes himself to be a grain of seed is taken to a mental institution where the doctors do their best to convince him that he is not a grain of seed but a man; however, when he is cured (convinced that he is not a grain of seed but a man) and allowed to leave the hospital, he immediately comes back, trembling and very scared—there is a chicken outside the door, and he is afraid it will eat him.“My dear fellow,” says his doctor,“you know very well that you are not a grain of seed but a man.” “Of course I know,” replies the patient, “but does the chicken?””