There was one scene from all the Star Wars movies that George Lucas and Irvin Kershner made Mark Hamill keep from everyone including his co-stars, and it was the infamous moment when Darth Vader reveals he is Luke Skywalker’s father.
The three men knew if it somehow got out, it would be Hamill that leaked it. So mum was the word for over a year and a half. He says he made sure not to tell Carrie Fisher because she could not keep a secret. In fact, he told Graham Norton that Harrison Ford and him would purposelessly tell her stuff to see how long it would take for everyone know. Talking about Han Solo, what was his reaction when he heard James Earl Jones say, “I am your father,” at the premiere screening? Hamill did a spot on Ford and said he leaned over to whisper in his ear, “Hey kid, you didn’t f*cking tell me that?” And with that Hamill was finally free to talk about that secret to anyone who asked.
BTW how much do you just love Hamill after this interview? He is just gosh darn lovable like an Ewok, BB-8 or a Porg.