In the grand history of Star Wars, there's always been one constant. Not the Force, not lightsabres or Skywalkers, not droids or spaceships even... The one thing that has really defined Star Wars is creative structure. When George Lucas was involved, he was singularly committed to his vision (to the point of reductiveness, in fact, some might say) and since Kathleen Kennedy has been at the top of the hierarchy, she seems to have preached a model of constancy.
There is an idea of what a Star Wars movie HAS to be, what the characters must be like and how things must be done. That's why Rogue One required such editing work and more pertinently it's why Phil Lord and Christopher Miller were removed from Solo even after it had begun filming. In both cases, the directors weren't really getting what they needed to do.
But Solo's directorial change is a strange one in light of an infamous Star Wars urban legend - and one of the most happily parrotted fables from a Star Wars set. Considering the pair were apparently let go because of their commitment to improvisation (even though they covered it with more rigid takes as well), the fact that one of Star Wars' most famous lines ever was supposedly improvised seems a little... contradictory to say the least.
There's a reason for that though: it's because the idea that Harrison Ford improvised the "I know" response to Princess Leia saying "I love you" in Empire Strikes Back might well be the biggest lie in the history of the franchise.
While it's true that Ford came up with the line, the idea that he said it in the moment while shooting is simply not accurate, no matter how devastating that is to the mythos around Ford's performance and the character. And indeed, the change to the script was the source of some consternation on the set precisely because it was planned in advance of shooting.
Journalist Alan Arnold was on set the day that the changes were made, when Ford came up with the line and spoke to director Irving Kershner about it and he was wearing a mic that recorded the very conversation (which was then transcribed by Secret History Of Star Wars):
Ford: I think I should be manacled. It won’t stop the love scene. I mean I don’t have to put my arms around Leia to kiss her. I can’t see how they would indulge in more than a straight kiss in such circumstances. It has to be rough and briskand over with.
Kershner: Absolutely. I don’t intend to mess around…”What’s up, buddy boy?”… in the love scene.
Ford: As I pass by her, I think Leia ought to say very simply, “I love you.”
Kershner: (Tries it out) “I love you.” And you say, “Just remember that, Leia, because I’ll be back.” You’ve got to say, “I’ll be back.” You must. It’s almost contractual!
Ford: If she says “I love you,” and I say “I know,” that’s beautiful and acceptable and funny.
Kershner: Right, right.
Thus an iconic moment was born. Not while the cameras were rolling, but before there was even a chance to rehearse the scene with the new lines. Ford deserves the credit of course (and his line is MUCH better than Kershner's), but discussing line changes and improvisation are not the same thing.
And unfortunately for Ford and Kershner, Carrie Fisher was less than happy with the changes, who shouted at them both (according to the transcription)
"...now I have to perform at half an hour’s notice scenes that have been all changed... All I’m asking is to be invited to watch you guys get a scene together. It may not center around me, like this one doesn’t, but I’m involved in it."
At least she clearly agreed to go along with it, because that line ended up being one of Han's greatest ever moments. But we should maybe all stop saying that it was improvised.