He and Yaphet Kotto stole every scene they were in, IMO.
I think the chestburster scene anecdote has been altered over the years. Considering the logistics of setting up the scene and only then filming it, the other actors obviously had to have known what was coming, but hadn’t been told exactly how literally gory it was going to be. Veronica Cartwright’s visceral reactions were especially rewarding for Ridley Scott.
Has anyone ever noticed how much Harry Dean Stanton looked like Alice Cooper? Just wanted to throw that out there for no particular reason.
Damn, but he is going to be sorely missed! I think all the times I watched Repo Man were to see HDS doing what HDS did best.
I just looked - he has 4 credits (including 5 Twin Peaks episodes) in 2017. Including one in post-production. The man worked on film for 63 years!
StG
I’m a little late to the party but can’t let it pass. Repo Man and Paris, Texas were two of the best films from 1984 and personal favorites. His small role in The Green Mile almost stole the film.
RIP, Harry Dean. You will be missed. 
And his scene in that same year’s Red Dawn was a bright spot in an otherwise-crappy film.