"Originally, I was trying to have the story be told by somebody else (an immortal being known as a Whill); there was somebody watching this whole story and recording it, somebody probably wiser than the mortal players in the actual events. I eventually dropped this idea, and the concepts behind the Whills turned into the Force. But the Whills became part of this massive amount of notes, quotes, background information that I used for the scripts; the stories were actually taken from the Journal of the Whills."
The Whills are, in fact, the species that the Star Wars saga is being told to, by the character R2-D2. This idea was conceived by the film's creator, George Lucas. Even though it ended up being unused in the films, it was alluded to in the novelization by Alan Dean Foster, in which the events preceding the book itself are from the "Journal of the Whills".
In the book The Making of Revenge of the Sith, it was revealed that the Whills are still a part of the Star Wars (at-the-time) canon. Because of this information, it is in fact R2-D2 who is the central character in the series, not Anakin Skywalker as most would speculate. R2-D2's relating the story to the Whills explains away the "a long time ago" setting that precedes each film and several of the games.
In the novelization of Star Wars Episode III: Revenge of the Sith, there was a passing reference to a Shaman of the Order of the Whills.
There are some who speculate that the Whills might be the same as one of the species that was actually featured onscreen in the franchise.
One such speculation holds that they are in fact the mysterious species that the Jedi masters Yoda, Yaddle, and Vandar Tokare belong to.
Another idea is that the Whills are spotted in The Phantom Menace, in the Senate Rotunda. The creatures are of the same species as "E.T.", the extraterrestrial from the 1982 film E.T. the Extra-Terrestrial.
Science fiction writer Algis Budris, writing in Asimov's Science Fiction magazine in 1981, jokingly referred to the closing medals ceremony scene in Star Wars (1977) as "The Triumph of the Whills" - implying that the scene resembled Leni Riefenstahl's 1934 documentary, Triumph of the Will, a propaganda film which depicted the Nuremberg rallies.