Inside the editing of 'Avengers: Endgame,' which included drastic changes to Black Widow's big moment and the time-travel scenes

During the "time heist" portion of "Endgame" the Avengers go back to important moments in the past to retrieve the Infinity Stones. In one instance, they go back to New York to get the Tesseract right when the Battle of New York is taking place from the first "Avengers" movie.

But a decision had to be made about what point they return in the battle that audiences would instantly recognize. It was not figured out until post.

"The script had us showing up right when Tony flies through the Leviathan and blows it up from the inside," Ford said. "But when we screened it for audiences in test screenings we realized it took a few minutes for them to acclimate themselves. It wasn't landing the way we wanted. So we tried other versions."

Ford said he cut one sequence where the entry point is the scene where Hulk grabs Loki and smashes him back and forth on the ground like a rag doll. But another moment from the movie won out.

"The version that won was where we come in on the Avengers first assembling, the round-a-round shot," Ford said. "It was the cleanest and most epic transition back into 'Avengers 1.'"

Ford and Schmidt had to dive deep into the archives for two great shots from the section of the movie when Thor and Rocket go back to Asgard to retrieve the Aether.

"The shot of Loki throwing his cup in the cell and Thor and Rocket sneak past him in the background, that's a piece of digital negative taken from the dailies of 'The Dark World' that we repurposed," Ford said. "The same for the scene of Natalie Portman."

Ford said the goal with all the jumps back in time in "Endgame" was to use as much footage from those original movies as possible. So in the case of Portman, she didn't have to step on set once to be in "Endgame."

Ford became a part of MCU history after the Russos revealed in an interview that he was the one who came up with Tony Stark's memorable "I am Iron Man" line to Thanos after he snatches the Infinity Stones from him. And according to Ford, the idea came after looking at many versions of the sequence.

"We shot it in a couple of different ways in the initial shoot with different lines of dialogue," Ford said. "Robert [Downey Jr.] also does an improvisation. We did some where he's just silent and one of those was our favorite for a long time. But we decided Thanos needed a moment at the end of the movie where he says something."

Ford said that in the original concept of the scene Thanos didn't say anything, it is just revealed when he snaps his fingers that he doesn't have the stones and that Stark took them.

"We thought there's this structure of the movie where Thanos says he's inevitable — he says it in the beginning of the movie and he sees himself say it in the middle of the movie," Ford said. "So we thought this could create this incredible symmetry if we carried that moment forward."

So once the "I'm inevitable" Thanos line was put in, the "I am Iron Man" line (which Downey Jr. came back to film in reshoots) was born to counter it.

Ford has got a kick out of the attention thanks to the Russos shoutout, but he's realistic about it.

"I've pitched some crazy bad stuff and they shot it down right away," he said with a laugh. "But if you don't say it you never know."

If you stuck around until the very end of the credits of "Endgame" you found something very unfamiliar for an MCU movie: not a single scene appeared. Instead, there was the sound of a hammer hitting metal while the Marvel Studios logo appeared on the screen. The sound is from the first "Iron Man" movie in 2008, as Tony Stark creates his first Iron Man suit. It pays homage to the movie that launched the MCU.

According to Ford, the hammer sound was an idea Marvel Studios head Kevin Feige suggested during post production of "Endgame."

"We knew early on that we weren't going to have any post credit scenes in this movie," Ford said. "Towards the end of our mix, Kevin came in and said, 'I got an idea, and I want to try it, what if we have a little audio flashback at the end with Tony?' So we dug through the elements of 'Iron Man 1' and found the exact piece of sound from the print master. We laid it in against the logo and adjusted the rhythm slightly. We showed Kevin and he gave it his blessing. We thought this was a great sendoff."