5 ideas
Young Thurber's army cot tips over in the dark with a crash, and his mother, sure the heavy old bed has fallen on his father in the attic, screams to rescue him. A trivial physical accident becomes a house-wide catastrophe because each sleeper reads the noise through his or her own standing dread.
In the 1913 Columbus flood a false rumor that the storage dam had burst sent thousands of residents running east, shouting "Go east!", with no one knowing who started it or why. A crowd's fear sustains itself, because each runner treats the other runners as proof of the danger.
Thurber's relatives each carry a fixed obsession, such as burglars, electricity leaking from empty sockets, or dying in one's sleep. Read this way, household chaos is not bad luck but the collision of several people's defenses against dangers that are not there.
In an Ohio State botany class, Thurber could never see plant cells through the microscope, to his instructor's mounting fury. When he finally drew something with confidence, it was the reflection of his own eye in the lens. This makes a precise emblem of an instrument meant for objective observation that returns only the observer.
Thurber recounts the wildest events in flat, bewildered, matter-of-fact prose and never signals that anything is funny. By treating his grandfather's belief that the Civil War is still on, or his family's panics, as ordinary facts, he forces the reader to supply the incredulity. The comedy lives in the gap between the calm tone and the chaos being described.