Wookiepedia:
"Midi-chlorians were first conceived by George Lucas as early as 1977. In this time the first Expanded Universe products were being created, including the ongoing Marvel Star Wars series and Alan Dean Foster's novel Splinter of the Mind's Eye. Lucas sat down with a member of his staff, Carol Titelman, to dictate a number of guidelines for these works, explaining various concepts of his universe. Amongst them were an explanation of midi-chlorians, which Force-sensitive beings were said to have more of in their cells.[31] However, Lucas did not feel he had the time to introduce the concept of midi-chlorians. The idea would not appear in any Star Wars product for twenty-two years; Lucas chose 1999's Star Wars Episode I: The Phantom Menace as the opportunity to first mention the midi-chlorians, explaining why some were sensitive to the Force while others were not, an issue that he had left unresolved since the original film Star Wars."
Elvileg a The Making of Star Wars könyben is van erről szó. Innentől kezdve tipikusan az a téma, amit aki akar, elhisz (ld. hány más, korábban elvetett öltet, név került bele a filmekbe utólag), aki meg nem akarja, az úgyis morogni fog miatta még 20 év múlva is. Csak a tipikus helyzet