Thurber's stories are characteristically infused with a dark comic tone. He rejected the term "humorist," which he called a "loose-fitting and ugly word." He said of writers such as himself that to call them humorists was "to miss the nature of their dilemna, and the dilemna of their nature. The little wheels of their invention are set in motion by the damp hand of melancholy."
We certainly see this in "The Night the Bed Fell." The situation is confusing and choatic because the individuals involved in it are confused and prone to chaos. The strange assortment of characters, including Thurber's mother, father, brother, cousing Brigg, and the dog Rex, are all described in peculiar detail. Briggs keeps a bottle of camphor near his bed in case he can't be awakened in the middle of the night. The dog is surly. The father makes a production of going off to sleep in the attic.
It is hardly surprising that such characters when thrown together would create bedlam. Thurber's tone as narrator is one of detached bemusement, a fond remembrance of events that seemed alarming at the time but now it has all been cleared up and we can all have a good laugh. The joke is on him, and them, and us, for we can all identify with the beleagured figures of Thurber's fact and fancy.