In Star Wars: The Empire Strikes Back, Luke Skywalker famously discovers that Darth Vader is his father.
Soon, he also comes to the realisation that the villain is Leia Organa’s (Carrie Fisher) father too – meaning the two are related.
This means the kiss they had previously shared was somewhat gruesome in retrospect.
Now Hamill has poked fun at the plot beat on Twitter.
A fan shared a black-and-white photo, seemingly from the set of Return of the Jedi, of Hamill looking horrified.
They asked: “Hi @HamillHimself I’m somewhat curious about this picture? What happened here? All the best, Jessen.”
Hamill responded: “The moment I realized I kissed my sister. #Innocestuous.”
During an appearance on US TV show The View last year, Hamill had recalled Fisher’s reaction to the twist.
He said: “So I remember… when they took us aside and said, ‘ok nobody knows but in this episode you’re going to be revealed as brother and sister’.
“And we were sort of shocked – and I thought for a minute, ‘wait, if Luke is Leia’s brother – does that make me royalty?’ And she went, [snapping] ‘NO!’
“I said, ‘all right! I was just asking!’ So possessive of all that. She was adamant – ‘no way!’”
Fisher passed away in 2016, but she joins Hamill in the upcoming Star Wars saga finale The Rise of Skywalker thanks to unused footage from The Force Awakens and The Last Jedi.
This week the next phase of the Star Wars movies was confirmed when Bob Iger allegedly announced that Game of Thrones’ DB Weiss and David Benioff will be behind the as-yet-untitled 2022 film.
It won’t be part of the nine-episode Skywalker saga: that particular chapter closes with Rise of Skywalker in December.
And now it’s also unclear what the future holds for Rian Johnson’s previously-announced trilogy, which does not seem to be on Disney’s release slate at present.
Star Wars: The Rise of Skywalker is out on December 19.