The man who would go on to play Luke Skywalker posted the footage online, revealing neither he nor Ford had read the script at this point, long before they both became movie icons when the first "Star Wars" film was released in 1977.
Hamill also explained that he and Harrison had never met before when they were asked to try out together for George Lucas' new movie.
"My screen-test for @starwars w/ Harrison on the 1st day I ever met him," Hamill captioned the footage. "Neither 1 of us had read the script at this point, only this 1 scene."
"I asked George what kind of movie it was - 'Let's just do it, we'll talk about that later'. We never did talk about it later - we just did it."