This idea comes from the movie 500 Days of Summer through my brother-in-law who watched it. A ten-minute scene in the movie is split-screen with one of the main character's expectations for a party on one side with what actually happens on another. This concept struck my brother-in-law strongly enough that he sat down to write something about it, but didn't get much farther than the original idea.
I, too, was inspired by this idea and have not been able to write anything about it. I like the idea of one side showing a person's average day while the other side shows the day dreams that the character is having about the same experiences. For example, one side might show the character's normal commute while the other side shows the character dodging the wreckage of an airplane that is crashing and causing havoc on the freeway. One might have a driver cut off the main character while the day dream shows the main character pushing a button that activates a hull-mounted auto-cannon that blows the offending driver off the road (... I may have had the day dream a few times ...).
In general, the movie would be about the numerous heroic or romantic fantasies that dance about our minds during otherwise mind-numbing experiences that fill our days. It might be a little too "meta" as it is a film (which is escapism) showing a person's escapism.