DAY-DREAMERS, space-cadets, dim-witted are terms used variously to describe those who routinely and effortlessly drift into fantasy realm - even in the midst of company and conversation.
To these drifters, the physical and the illusory worlds co-exist.
Calling someone a day dreamer summons an image of one who is lazy and ineffectual but I would argue that conjuring fantasies is actually a complex mental process not for those accustomed to mental sloth. Each fantasy typically involves the orchestration of a story line with intricate character casting, scripting, and location visualizing. It's a virtual and vicarious life.
Walter Mitty has the required intensity, intelligence and introversion that makes it easy for him to indulge in fantasies that gratify his emotional, intellectual and social needs. That gratification is real even if the imageries are not.
At best, wool-gathering is an effective way to cope with a life of sheer banality, and to the itinerant mind tripper, a life of having been there, done that!
In the case of Walter Mitty, a romantic interest gives him the courage to move out of reverie into reality, and subsequently, the castles in the air lose their lustre.
On the whole, a lovely year-end movie with visual effects that are are brilliant and stunning.
Go see it!