In the movie "Stranger Than Fiction" the professor of literature makes quite a big deal about the phrase "little did he know."
I've written papers on "Little did he know." I've taught classes on "Little did he know." I once gave an entire seminar based upon "Little did he know."
Is this phrase as relevant and studied in writing as it is implied in that movie?
While it's true that the phrase has no great significance, it does have connotations associated with slightly old fashioned fairy-tale style narration, such as you might find in Alice and Wonderland, Pooh Bear, Grimm's Fairy Tales, etc.
You probably wouldn't use the phrase in regular writing unless you were making a deliberate ironic nod in this direction, which is what the narration style in Stranger than Fiction does.
The comment about once giving an entire seminar on this phrase is a lighthearted joke at the expense of English Lit academics who have a reputation for massivily overanalysing the smallest aspects of litrature and writing.
Whenever you write "little did (s)he know" in fiction, you're probably writing too much from the omniscient author perspective, rather than from the character's perspective. This may indicate a violation of the "show, don't tell" rule.
The phrase is being used here to refer to what is commonly called either Sophoclean irony or Dramatic irony, a literary device in which the reader knows something that the character does not -- something which is going to have a material effect on the character's future. This device is extremely useful as a way to build tension and to manipulate the reader's emotions, and therefore very important in literature.
The most easily recognizable form of Sophoclean irony is the horror movie in which the audience sees the killer hide in the attic, and then later the cheerleader and the quarterback sneak up to attic for a little extracurricular activity. The characters think they are going to get lucky. The audience know they they are going to get julienned.
Another example that springs to mind is from the Downton Abbey precursor Upstairs Downstairs in which we see beloved characters boarding a ship for America and in the final (season ending) shot, the camera pans round to the name of the ship: RMS Titanic.
So, the professor is giving lectures and entire seminars on Sophoclean irony, and yes, it is a big deal. Using the phrase "little did he know" is simply a way of simplifying a complex idea for an audience who mostly has no interest in literary theory. (Ironically, a case of the character knowing more than the reader does.)
We all change. When we look back, the phrase applies. One a change in awareness or perception happens, we look back on our unawares self, "little did we know."
The phrase "little did he know" has no particular significance to English Literature or writing in general. The only reason that it was significant in that movie is because the author character had a penchant for using the phrase, and the professor was able to use it to identify the voice in Will Farrell's head.
