Via Yahoo.com:
Can you call it a spoiler if someone reveals the plot to a movie that won’t be made for another 30 years?

Thirty-five years ago today, The Empire Strikes Back made its debut in theaters. Before its release, Star Wars fans had no idea that Darth Vader was Luke’s father, and were totally in the dark about the big bad Sith Lord’s backstory… unless they happened to catch a 1980 TV interview with Mark Hamill (which you can watch above).

“Twenty years earlier, in the third story, you see how Darth Vader came to power and fell from grace, and how the Obi-Wan character battled with Darth, and why he was forced to wear this mask,” Hamill says, casually explaining the climax of Revenge of the Sith, a film that would come out more than three decades after this interview aired.

He adds that “there’s an 8-year-old Luke running around, playing in the background” of that still-theoretical prequel. That obviously didn’t happen, and for good reason; if Luke was that old when Anakin went fully to the Dark Side, the young Jedi would probably not have been so surprised when Vader broke the paternity news to him all those years later.

There has long been a debate about just how much backstory Star Wars creator George Lucas had plotted out in the franchise’s early days; in 1980, he told the sci-fi-focused Prevue magazine that he had plotted out 12 movies, which he later whittled down to nine. That included three prequels to Star Wars: Episode IV — A New Hope, though it’s always been fuzzy regarding when Lucas finalized the saga’s major details: In this transcript of a conversation he had with Empire co-writer Lawrence Kasdan reveals that he had by then decided that Anakin was the father of Luke and Leia.

One interesting note from that transcript: Lucas says that anyone can be a Jedi, whereas later on, usage of The Force is dependent on Midichlorian count.

The video above also briefly reveals some early plan for the third trilogy, Episodes VII-IX. Harrison Ford tells the interviewer that he didn’t think that Han Solo would be in those films, which would instead follow a new cast of characters. As we know now, Lucas gave Disney his plans for the next trilogy when he sold Lucasfilm to the Mouse House in 2012, but director J.J. Abrams decided to mostly construct a new story from scratch — one that includes Han Solo.