“Star Wars” icon Mark Hamill revealed over the weekend on Twitter that the end of filming “The Empire Strikes Back” was especially tough on him ― because he had to keep one of the industry’s biggest secrets for more than a year.
And he couldn’t even tell his co-stars.
On Sunday, Hamill retweeted a fan’s post featuring a behind-the-scenes image from the film’s climax, where his character, Luke Skywalker, learns that Darth Vader is his father. The actor said a different line was spoken on the set to keep the plot twist a secret ― which led to a year of “agony” as he had to keep it under wraps until the film’s premiere:
The cast & crew first learned of it when they saw the finished film. When we shot it, Vader's line was "You don't know the truth, Obi-Wan killed your father." Only Irvin Kershner, George Lucas & I knew what would be dubbed in later. Agony keeping that secret for over a year! 😩 https://t.co/DcB2lW8AhC— Mark Hamill (@HamillHimself) May 24, 2020
Hamill went into more detail on keeping the secret in a 2017 interview with the BBC that included a pitch-perfect impression of Harrison Ford learning about Luke’s parentage while watching the film for the first time.
Hamill has been sharing his “Star Wars” memories all month on Twitter, often playing off the “May the Fourth be with you” theme of Star Wars Day on May 4.
Also on Sunday, he shared a gif of a scene that had to be reshot because they changed the character’s last name later in production:
May The 24 Be My Age When We Had To Reshoot The Imprisoned Princess Scene In #StarWars Because The First Time We Filmed It I Said: "I'm Luke Starkiller, I'm Here To Rescue You."#TrueStory pic.twitter.com/FVJiwxpONL— Mark Hamill (@HamillHimself) May 24, 2020
CORRECTION: This article previously stated that Hamill “botched” his character’s last name in the scene that was reshot. According to Hamill, the scene was reshot because the character’s name was changed later in production.
This article originally appeared on HuffPost.