"Chris and Chris, this is like a radio show!"
[Bucky’s] also got this kid he has to look after, which he’s always had as family – he doesn’t want to ruin that image of himself that Steve has, so that’s a conflict for him, because he’ll go to the end of the world to protect him. […] They’re both orphans, they’re essentially like brothers, they’re the only family they’ve got, they look out for each other, they pick on each other. Sebastian Stan
Joe Russo: We always said that the whole movie lives or dies on that last scene between him and Bucky. You know, this third act is a fait accompli in a way. It’s a superhero movie.
Steve McFeely: I suspect he will win.
Joe Russo: The expectation is that he will win. But the real story is will he win Bucky, will he save his friend, will his friend kill him, will he have to kill his friend? The tragedy of that moment was the most important thing to us as directors in the third act. That’s the real climax of the act.
Steve McFeely: Yeah, from jump street we always worked towards getting to: “I will sacrifice myself in order to reach my friend.” And so “end of the line” has been the line since the very beginning. And Sebastian nails it, it cracks him.
Chris Markus: Again, it’s about Steve trying to save his past.
Joe Russo: It’s the last thing he has left.
- Captain America: The Winter Soldier Blu-ray Audio Commentary