37 things we just learned about the making of 'Avengers: Endgame' that answer some pivotal questions about the movie

Warning: There are spoilers ahead for "Avengers: Endgame."
The "Endgame" home release is filled with special features and a three-hour commentary from the movie's directors and screenwriters.
From how Natalie Portman's "Endgame" scene came together to some alternate versions of key scenes, INSIDER rounded up what you probably didn't know about the making of the film.
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"Avengers: Endgame" is finally available to watch at home on digital HD.

In addition to six deleted scenes and a gag reel, the film comes with a few special features with producers and Marvel Studios' president Kevin Feige.

The best part of the home release fans will want to check out is a three-hour audio commentary to the "Avengers" sequel that provides insights into how the highest-grossing movie of all time came together. "Endgame" directors, Anthony and Joe Russo, and screenwriters, Christopher Markus and Stephen McFeely get together to share the evolution of key scenes, how Hawkeye was almost in "Infinity War," and alternate versions of scenes with Nebula, that were once on the drawing board.

Before its Blu-ray release on Tuesday, August 13, INSIDER rounded up some of the best behind-the-scenes details revealed on the "Endgame" audio commentary and special features.

Marvel had a fake version of the "Infinity War" and "Endgame" scripts that they referred to as "code blue."

"We knew from the start with 'Infinity War' and 'Endgame' that these two movies were going to be the biggest in terms of security level, that we needed to protect the content," said executive producer Trinh Tran on an "Avengers: Endgame" special feature.

In order to keep secrets hidden, the only actor who received a full version of the script was Robert Downey Jr. In addition, the Marvel team had fake and real versions of the script. According to Tran, they referred to the real script as "code red." The fake version of the scripts were referred to as "code blue."

Marvel Studios' president Kevin Feige says the majority of the script stayed the same. They just changed "a few key things," including the moment where Loki died in "Infinity War" and when Thanos lost his head in "Endgame."

The opening scene of "Endgame" with Jeremy Renner was originally near the end of "Infinity War."

"Endgame" opens right before Thanos snaps his fingers and wipes out half of all living things in the universe. We see Hawkeye lose his entire family, unaware of what just occurred.

"This scene was supposed to be in 'Avengers: Infinity War' after Thanos snapped his fingers," said codirector Joe Russo on the film's commentary. "We thought it might be interesting to cut to a verite scene between Hawkeye and his family."

The Russos thought it was too disorienting and busy to have at the end of "Infinity War" when they were already cutting between people disappearing in Wakanda and in space. The start of "Endgame" wound up being the right fit for the scene to remind viewers what happened at the end of "Infinity War" and how you felt.

Visual effects were used to make Tony Stark look emaciated at the film's start in space.

As Tony leaves a message for Pepper Potts, he looks like he has lost a significant amount of weight. Robert Downey Jr. didn't really lose weight for the movie's opening scenes.

"Our VFX team did an exceptional job of taking some weight off of him and making him look like he is on death's door," said Joe Russo.

"The intent here was to make you believe, if momentarily, that we may actually kill Tony Stark at the beginning of the film," he added.

If you were confused about how Captain Marvel was able to find Tony and Nebula, there's a simple explanation.

If you saw "Infinity War," one of the end-credits scenes shows Nick Fury page Carol Danvers. According to the Russos, Captain Marvel then traveled to Avengers HQ, as seen at the end of "Infinity War," found out what Thanos did, and went off to space to find Tony and Nebula.

"The missing narrative is that she came to Earth, met the Avengers, was brought up to speed on what was happening, and that there's some sort of homing beacon on that ship that she tracks," said Joe Russo.

In an earlier version of the film, we wouldn't have seen Carol Danvers revealed until after she brought Tony and Nebula back from space.

"We felt like it was not as successful of a reveal," said Joe Russo. "We didn't like the transition."

"[Tony would] see something. The audience wouldn't see it, and then only would you reveal what happened there," screenwriter Christopher Markus said of showing Captain Marvel as the spaceship was shown landing back on Earth.

There was a hint at Thor's oncoming depression early in the film that you may have missed.

While Tony and Steve Rogers are bickering, Thor can be seen in the background eating from a bowl of bread. That was a hint at his weight gain to come in the flash-forward.

"He's chomping on a bread roll, if you notice," said codirector Anthony Russo. "Hemsworth wanted to eat something in this scene."

The Russos and screenwriters joked that the fate of the world really came down to the rat letting Scott Lang out of the Quantum Realm.

In "Infinity War," Doctor Strange saw more than 14 million outcomes where the Avengers lost against Thanos. The "Endgame" screenwriters and codirectors joked that the fate of the universe rested in the paws of the little rat who coincidentally let Scott Lang out of the quantum realm five years later.

"Here were 14 million versions of this story where the rat did not step on that button," joked Joe Russo.

Joe Russo said it made sense to show us life on Earth through Scott Lang's eyes because it would have more of an emotional impact on the viewer.

"When you have a character that is traditionally funny, and now they're, you know, they're surrounded by pathos, it makes it doubly emotional for you," said Russo of why we follow Scott Lang discover what happened on Earth as he wanders through San Francisco.

Screenwriter Christopher Markus says they originally thought time travel was a dumb idea.

In a conversation at the 92Y in New York City in April that INSIDER attended, screenwriters Markus and Stephen McFeely said they wrote the "Infinity War" and "Endgame" scripts back-to-back.

On the "Endgame" commentary, Markus said it was tough to figure out how to get themselves out of the corner they backed themselves into at the end of "Infinity War."

He said they entertained the idea of a time machine, but then felt it was "the stupidest idea you could possibly have" to resolve the Thanos snap.

Markus said they then realized the "Ant-Man" franchise may not make that too far-fetched.

"The 'Ant-Man' franchise, which we hadn't dealt with yet, had legitimately, if you believe the science, the seeds of a time machine in it, which was a breakthrough," said Markus.

We almost saw Professor Hulk in "Infinity War."

"The creation of Smart Hulk used to take place in 'Infinity War,'" said McFeely.

In the 2018 film, Hulk and Bruce Banner aren't getting along at all and when Bruce really needs the green guy's help, he refuses to come save the day. That moment forces Bruce to step up and be a hero and ultimately leads to the two working things out from there after the Thanos snap.

According to McFeely, we would have seen this new version of the Hulk fighting in Wakanda at the end of the last film when Bruce needed his help.

"And at his hour of greatest need, they make some sort of compromise, and Smart Hulk rips out of the armor and beats the crap out of Cull Obsidian and destroys him," said McFeely of the alternate scene that could have taken place.

We didn't see Professor Hulk until "Endgame" because it would have been odd for Bruce to have a victory in "Infinity War" when everyone else was suffering major losses.

"The movie needed to just stay in its succession of losses in the third act, which meant some hustling on the part of VFX late in the game," McFeely added of how late that change was made to "Infinity War."

Joe Russo said the movie was even shown with the scenes to some test audiences and it wasn't working because the transformation happened too quickly.

The Russos say Tony Stark thought of Peter Parker as his other child.

If you've watched "Spider-Man: Homecoming" or "Captain America: Civil War," it's clear Tony cared a lot for Peter, even if he didn't always show it. In "Endgame," we learn Peter was so important to Tony that he kept a photo of him near his father, Howard Stark, in the kitchen for years, as if he was a member of the family.

While he served as an unspoken fatherly-type figure to Peter in the MCU, it was never directly addressed in any of the movies. On the film's commentary, the Russos make the father-son connection between the two very clear.

"This is like his other child that he's lost," Russo said of how Tony views Peter. "[That] spurs him to action. [It] makes him consider that, you know, even though he has this child [his daughter, Morgan], he still lost a child, and there may be potential to bring that other child back, and he's now in conflict."

Hawkeye is traveling the world killing bad guys as a way to make sense of what happened to the world.

Seeing his entire family vanish right in front of his eyes, sent Hawkeye down a path of vengeance. When we see him about an hour into the movie, he has a new look and is mercilessly killing men in Tokyo. He's on a one-man mission.

"He's traveling the world punishing bad people who survived the snap. This is a way for him to feel some sort of purpose even though it is a dark purpose."

Bruce Banner's explanation of time travel is straight from a quantum physicist.

Marvel's time travel in "Endgame" isn't something that was just made up.

"[Banner's] explanation is essentially what we were told by genuine quantum physicists brought into the writers' room to explain time travel to us," said screenwriter Christopher Markus.

A timer was put on Hawkeye's time travel suit on purpose when he tried it out.

Director Joe Russo said the Avengers wanted to make sure he didn't decide to stay in the past with his family.

We could have seen Hawkeye attack Professor Hulk after coming back from the time travel stint.

"We did a version of this scene where Hawkeye attacks Smart Hulk because he's so angry about being pulled back," said codirector Anthony Russo.

Instead, Black Widow runs right up to Hawkeye when he returns and Clint Barton simply tells everyone that the technology worked.

A deleted scene shows Rocket Raccoon watching the Battle of New York from "The Avengers."

Rocket's extremely confused when he finds out the Avengers spent hours fighting Thanos' Chitauri army.

"The Chitauri are the suckiest army in the galaxy," Rocket said in the scene. "Why didn't you just blow up the mother ship?"

As Rocket continues to critique the group, Tony Stark comes up behind him and shaves off part of his head.

The screenwriters make it clear that Nebula didn't know what you need to do to get the soul stone.

One of the questions we pondered while watching the film the first time around was whether or not Nebula knew that someone had to sacrifice themselves in order to get the orange Soul stone.

Nebula was the only one left alive after the Thanos snap who knew about its whereabouts. It seemed awfully convenient that she didn't volunteer to get the stone herself even though she knew a lot about it. From one perspective, it made it look like she let Hawkeye and Black Widow go willingly knowing that someone would sacrifice themselves.

Apparently, that wasn't the case at all.

"Nebula doesn't know about the exchange that's required at Vormir," said McFeely. "No one knows other than anybody who was there. She just knows her sister didn't come back [at the end of "Infinity War"]."

The screenwriters have thought about Captain America running into Red Skull when returning all of the Infinity stones at the movie's end.

After the Avengers save the world, Captain America volunteers to return all of them to the exact moment in time when they first stole them.

It's not mentioned in the movie, but that would lead to an awkward reunion of sorts for Cap when returning the soul stone. Cap doesn't know that his old foe Red Skull (from the first "Captain America" movie) is the keeper of the Infinity stone on Vormir.

The scenes with Thor and Rocket Raccoon traveling back in time were filmed years prior while making "Infinity War."

McFeely says the scene was shot at Durham Cathedral in April 2017. It was one of a few scenes shot for "Endgame" during the filming of "Infinity War."

The running gag about Captain America's behind may not have made it into the final film.

In the movie, Ant-Man refers to Captain America's butt as "America's a--," and it quickly became a stand-out moment in the movie among fans.

Codirector Joe Russo referred to it as the "most controversial joke" in the movie that was hotly debated.

The scene of Natalie Portman getting out of bed in "Endgame," was from "Thor: The Dark World."

Portman didn't act out that scene for "Endgame." According to Joe Russo, it was an outtake from the second "Thor" movie.

"We added Rocket to the shot and changed the context of the original intention of the shot," said Russo.

Stan Lee did dress up as his younger self for the scene in 1970.

It was the last Marvel scene he filmed before he died in November 2018.

Read more:See every Stan Lee Marvel cameo

Originally, viewers wouldn't have known that 2014 Nebula was sent the future.

When 2023 Nebula gets kidnapped by Thanos, Gamora, and Nebula from 2014, we see Thanos send his loyal version of Nebula to 2023 to bring him to the future.

The audience originally wouldn't have known which Nebula went back to 2023, but that idea was ultimately scrapped.

"We kept this from the audience, the idea that Thanos was going to use his version of Nebula to replace future Nebula," said McFeely. "It didn't work. It was complicated and it was confusing."

The final version of the film was much more clear.

Hawkeye and Black Widow were the obvious choices for the screenwriters to go to Vormir.

It wouldn't have made sense to send Rocket Raccoon and Nebula. You need to sacrifice someone you truly love in order to get the Soul stone. They're friends, but they're not that close from what we've seen.

"A pair of people who could arguably love each other needed to go to Vormir for this to work," said Mcfeely. "This was the obvious pairing in our minds."

The scene with Hawkeye and Black Widow could've been different.

Screenwriter Stephen McFeely said it could've been a bit more complicated with Thanos getting into the mix.

"It was Thanos sending a small army to pretend to try to stop them," said McFeely. "It was sort of awkward."

Joe Russo confirms why Black Widow cannot be brought back after her death.

Many simply thought that either the time machine or the time stone could be used to save and bring back Black Widow after she sacrificed herself. Russo says the rules of the soul stone make her death permanent.

"Red Skull very clearly says, 'It is an everlasting exchange," said Russo. "Everlasting would imply that it can't be undone."

We will get to see more of Black Widow's story in next year's standalone movie featuring Scarlett Johansson.

Only few people in the Marvel Cinematic can successfully wear and use the Infinity Gauntlet.

"It permanently damages the most powerful beings and some of the most powerful creatures in these movies," said Joe Russo. "Very few people can actually put that on and survive."

Seeing both the Hulk and Thanos damaged after using the stones is set up for the movie's final hour. It's heavily hinted ahead of time twice that a regular human can't wield the stones and live to tell the tale.

There was an early version of a script that showed 2014 Thanos with a decapitated Captain America.

Screenwriter Christopher Markus said there was another version of the script where Thanos would have opened up a large portal on the battlefield to come to 2023.

"He walked up to [the Avengers] and tossed 2012 Captain America's head on the floor," said screenwriter Christopher Markus.

"For a movie that began with essentially Thanos' head on the floor, it was a shocking reversal, but perhaps a bridge too far," he added.

Anthony and Joe Russo talked about the shocking moment with Entertainment Weekly in July, saying that 2014 Thanos would have gone back in time to murder all of the Avengers in his timeline.

It's hinted at why Thanos was easily able to dismantle Cap's unbreakable shield.

Captain America's shield is supposedly to be virtually unbreakable. It's built from the strongest metal on Earth, but Thanos is able to chip away at it quite easily with his sword.

The screenwriters confirm it doesn't seem like Thanos' sword is made of vibranium.

"While vibranium is the strongest substance on Earth, whatever Thanos' straight razor there is made out of is stronger," said Christopher Markus.

"Well, Thanos clearly knew of Eitri," said Joe Russo, noting the character who built him the Infinity Gauntlet in the last film.

Out of all of the heroes, Scarlet Witch is named one of the most powerful superheroes during the movie's big fight.

Scarlet Witch watched Thanos kill Vision in "Infinity War" and she goes after him in "Endgame" to get her revenge. She comes the closest of any hero to finishing him, and without any help.

"She's really the biggest threat to Thanos on this field," said McFeely.

"She's a very powerful character," added Joe Russo. "And [Thanos] has to, in a way, cheat and sacrifice his own armies just to escape her."

In "Endgame," Russo said she's even more powerful because the pain caused by Vision's death accelerated the growth of her power. Scarlet Witch will be back in one of Disney Plus' upcoming shows, "WandaVision."

There's a reason Tony Stark doesn't die the moment he gains control of the Iron Gauntlet.

We saw what the gauntlet did to Bruce Banner when he put the glove on. He was in excruciating pain. Tony's able to have a conversation with Thanos before snapping his fingers.

"His suit is keeping him alive here," said Joe Russo of Stark's technology. "But when he snaps those fingers..."

"It's too much," added McFeely.

Russo said the shot of Stark snapping his fingers was the last one they shot for "Endgame" during reshoots in January 2019. That was four months before the film came out.

The team thought a lot about how Tony should look in his final moments.

Joe Russo said they knew Tony's face would be half destroyed after using the gauntlet, but a lot of consideration went into how damaged it should look for the audience.

"If it's too far, you can't look at it," said screenwriter Stephen McFeely.

"If it's not enough, then you don't feel it," said Russo.

Robert Downey Jr. was adamant that Tony Stark stayed silent in the moments before his death.

Lines were written for Stark to say goodbye, but the team said Downey Jr. was insistent he didn't say a word.

"We scripted a lot of emotion and emoting and dialogue for him saying goodbye, and people saying goodbye to him," said McFeely.

Joe Russo added that it made sense. Using the gauntlet really incapacitated him.

The movie's most popular line, "I love you, 3,000," wasn't added until very late in the movie.

"We only came up with the idea for the 'I love you, 3,000' at the end of the movie in post," said Joe Russo.

According to screenwriters Christopher Markus and Stephen McFeely, the line was originally different. It was changed to 3,000 because of some inspiration on Robert Downey Jr.'s part.

During a conversation at the 92Y, McFeely said the original line was, "I love you tons." In real life, Downey Jr.'s kids say to him, "I love you, 3,000."

In case there was any doubt, Doctor Strange knew Tony Stark had to die to save the universe.

In "Infinity War," Doctor Strange tells Tony Stark there's only one version of events where they all beat Thanos.

"[Doctor Strange] knows exactly what's happening in that moment," said McFeely.

Looking back at the scene now, it's easier to see that. Doctor Strange apologizes to Tony saying it's the only way. We know now, he's not talking about letting Thanos snap away half the universe. He's also apologizing for knowing that Tony will have to sacrifice himself down the road.

One of the funniest deleted scenes shows Rhodey pointing out a huge plot point in the first "Captain America" to Steve Rogers.

Rhodey learns Steve Rogers was frozen in ice for years because he crashed a plane to save Manhattan. Rhodey thinks about that and asks Steve the question many fans have had.

"You couldn't have jumped out of the plane before you crashed it?" he asked.

Steve is never given a chance to respond, but it's something that probably weighed heavily on his mind since he thawed out.

The scene at the movie's very end with Peggy and Captain America takes place not long after he returns all of the Infinity stones.

You may have missed this on a first watch of the movie, but the house where Peggy and Steve are dancing has the door left ajar.

"This is very shortly after their reunion," Joe Russo said of the timing of the end of the movie.

"I imagine that about 10 minutes ago, [Cap] knocked on the door, she dropped whatever she was holding," added McFeely.