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The Avengers: Endgame Scene That Was The Most Difficult To Write

Actual science and science fiction have played a substantial part in the Marvel Cinematic Universe since the very first Iron Man movie. Thanks to films like Thor: Ragnorak, magic has also been pivotal, almost treated synonymously with its more realistic counterpart. Yet, no previous chapter of this sci-fi-infused superhero saga came close to the job of stitching together the Avengers' final mission. Time travel rested at the heart of Avengers: Endgame, from its beginning to its end — so much so that if the theoretical backbone of the film's time-jumping wasn't believable, the entire story would have unraveled.

The Endgame writers' hands were full with piecing together several technically and emotionally tricky team-ups and goodbyes, but creating the blueprint to take down Thanos (Josh Brolin) through time travel may have proven to be the most complex part of crafting Endgame's plot. During a livestream and Twitter chat on April 27, 2020 to celebrate the first anniversary of the blockbuster release, Avengers: Endgame co-writer Christopher Markus said as much. Not only did he pinpoint the exact moment in the script that tripped up him and fellow co-writer Stephen McFeely the most, but he also explained how writing the scene well was about more than getting the science right.

Avengers: Endgame's most difficult scene involved juggling science with entertainment

In Avengers: Infinity War, Doctor Strange (Benedict Cumberbatch) reveals that out of more than 14 million "possible outcomes" of the future, there's only a single timeline in which Thanos doesn't fail. When the surviving Avengers decide to go back in time, obtain the Infinity Stones from moments in the past, return to the present, and save the ones they lost in Endgame, they were going to have to pick the exact right time to secure each Stone before they ended up in Thanos' hands.

But there were so many moments across the MCU's then 21 films in which the Stones appeared that the task of choosing which time to drop these heroes into seems nearly impossible. According to one of Endgame's co-writer, it practically was. 

When a fan on Twitter asked Markus what scene from Avengers: Endgame was the most difficult to write, he pointed to the moment where the Avengers put their heads together and settle on a time travel plan. "More of [a] sequence than a scene, but the bit where they work out where to go when they travel through time," Markus said of the ensemble moment. What ultimately made the scene so complex was "trying to make the mechanics of time travel make sense, yet retain enough character to keep things entertaining," Markus explained. 

Captain America (Chris Evans), Iron Man (Robert Downey Jr.), Hulk (Mark Ruffalo), Ant-Man (Paul Rudd), Thor (Chris Hemsworth), Rocket (Bradley Cooper), Nebula (Karen Gillan), James Rhodes (Don Cheadle), Black Widow (Scarlett Johansson), and Hawkeye (Jeremy Renner) all end up time-hopping. While characters like Hulk and Iron Man are smart enough to figure out the science of time travel, the final decisions about when and where to get the Stones were determined by interactions of these specific personalities — all of whom had to explain the science without sounding like a walking, talking textbook. 

At the end, who was in the room when this plan came together had as much of an impact on crafting Avengers: Endgame's most difficult scene as what brought them there.