The Duke's unlikely inclusion in a galaxy far, far away came in the creation of the insect-like voice of Garindan, the long-snouted Imperial spy who totally narcs out Luke Skywalker, Obi-Wan and their droid friends to Stormtroopers.
"I always wanted to do an insect man - we didn't really have an insect man come along until Poggle the Lesser [from prequel Episodes II and III]," said sound designer Ben Burtt in 2007 to the StarWars.com blog. "We had that character that looked kind of like a mosquito from the first Star Wars [Garindan] that we found we needed a sound for. And I was wondering back a few months ago how I did it - because I keep notes and tapes - and I discovered it was an electronic buzzing which had come off of my synthesizer that was triggered by a human voice. And I listened to it and realized it was John Wayne - I had found some loop lines in the trash from the studio that had been thrown away. So the buzzing was triggered by some dialog like 'All right, what are you doin' in this town' or something like that."
Garindan's shining moment's a less ballyhooed scene from Mos Eisley than the one still sparking debate over who shot first: Han Solo or Greedo? Star Wars creator George Lucas' feelings about this are informed by Wayne's classic Western films with director John Ford.
"Han Solo was going to marry Leia, and you look back and say, 'Should he be a cold-blooded killer?' Because I was thinking mythologically -- should he be a cowboy, should he be John Wayne? And I said, 'Yeah, he should be John Wayne,'" Lucas said (as quoted by Legends Revealed). "And when you're John Wayne, you don't shoot people [first] -- you let them have the first shot. It's a mythological reality that we hope our society pays attention to."
Neither Garindan's vocal lines nor Han shooting last is the most blatant homage to Wayne in a Star Wars movie. That comes in the Episode IV scene where Luke rushes home to find his aunt and uncle dead, which borrows heavily from The Searchers.