Mitty is very much a Thurber protagonist, so much so that he has been called "the archetype for dreamy, hapless, Thurber Man". Like many of his male characters, such as the husband in "The Unicorn in the Garden" and the physically unimposing men Thurber often paired with larger women in his cartoons, Mitty is dominated and put upon by his wife. Like the man who saw the unicorn, he escapes via fantasies. A similar dynamic is found in the Thurber story "The Curb in the Sky", in which a man starts recounting his own dreams as anecdotes as an attempt to stop his wife from constantly correcting him on the details.
In his 2001 book The Man Who Was Walter Mitty: The Life and Work of James Thurber (ISBN 0-930-75113-2), author Thomas Fensch suggests that the character was largely based on Thurber himself. This is consistent with Thurber's self-described imaginative interpretations of shapes seen with his "two-fifths vision" in his essay "The Admiral on the Wheel". Neurologist V.S. Ramachandran suggests that Thurber may have had Charles Bonnet syndrome, a neurological condition that causes vivid and bizarre hallucinations even in blind patients.
Thurber's love of wordplay can be seen in his coining of several nonsense terms in the story, including the pseudo-medical jargon "obstreosis of the ductal tract", "streptothricosis", and the recurring onomatopoeia of "ta-pocketa-pocketa-pocketa." The medical nonsense that "coreopsis has set in" uses the name of a flower which sounds vaguely like a horrible medical condition.