“I love you.”
You know the legend about how Han Solo’s reply in Empire Strikes Back came to be? That Harrison Ford ad-libbed on set? It’s a good and often repeated story.
It’s also not true.
The truth, as is often the case, is more mundane. The director and Harrison met before they filmed the scene and talked about it, deciding to change the script. It was Harrison’s idea to say “I know,” which is likely where the legend comes from. The scene (#379) was shot on June 21, 1979 on Stage 4 (Carbon Freezing Chamber set) in Elstree Studios. We know this because the call sheets were saved.
The script, dated February 20, 1979, read as follows:
Leia: … I love you. I couldn’t tell you before, but it’s true.
Han: Just remember that, ’cause I’ll be back.
We know this because the script was saved. The director, Irvin Kershner, was wearing a mic that day, recording every word he spoke, and every word spoken to him (this was for a publicist working on a behind the scenes thing). We know this because the recording was saved.
The entire conversation is printed in The Making Of The Empire Strikes Back, by JW Rinzler, and it’s a fascinating read (the entire book is brilliant). Basically, Kershner had issues with the scene as it was in the script. Han Solo has “no idea what you’re doing there,” he says to Harrison. Later he says “See, I hate a scene where the bad guy waits and finally says, ‘enough of this horseshit, now let’s get on with it.’ That’s basically what this scene is.” One of Harrison’s suggestions for helping the scene? “If she said ‘I love you,’ I could say very nicely, ‘yeah, I know. Don’t worry I’ll be back.”
Their entire conversation is far too long to print here, but like I said it is all in the book (including the follow-up conversations between Kershner, Billy Dee Williams, and Carrie Fisher). The scene wasn’t ad-libbed on set. The scene came together via discussions with the main players involved and then they filmed it. It’s not a very exciting story, but it is the truth. Other lines in that scene which were made up in conversation prior to filming? Han and Lando’s “what’s going on” exchange, as well as the “he’s worth a lot to me” exchange between Vader and Boba Fett.