If Thanos lived in our reality, he'd probably find little to no fault with the Marvel Cinematic Universe, which continues to remain a thing of "perfectly-balanced" beauty (at least judging by the box office numbers). But, with so many interrelated moving parts, one major change or deviation could cause the entire system to collapse.

Avengers: Infinity War and Avengers: Endgame co-writer, Christopher Markus, pointed this out to Empire Magazine for the publication's May issue.

"The MCU continues to exist," he said. "What happens to be in it is a fluid and evolving thing where, because it's all connected, you can't reboot one. All the parts have to work together. Things continue, but like life, losses are real, and change is real."

The closest thing we've ever seen to a "reboot" in the MCU is the recasting of certain characters like the Incredible Hulk, Fandral, and Red Skull. Even so, these changes have been played off as natural elements that have always existed within this shared universe. No mention is made of a new actor in a familiar role. In a way, that's almost a load off of Disney's shoulders, which has set up such an expansive world, that tweaking a small part can fast be be assimilated into the whole and accepted by audiences.

Nevertheless, that seamless harmony displayed onscreen doesn't always translate to behind the scenes. Marvel Studios president Kevin Feige makes it look easy, but there are moments of incredibly great stress. For instance, he was feeling very confident in Infinity War's bleak ending (which was almost saved for the sequel) until panic began to set in shortly before the movie's theatrical release last spring.

"It was like, 'Wait a minute: what have we done?'" he told Empire. "For years, leading up to the release of that ending, people were going, 'These movies are predictable. The good guy always wins.' And for years I was thinking, 'Just wait.'"

Directed by Joe and Anthony Russo, Avengers: Endgame hits theaters everywhere April 26.

Markus co-wrote the screenplay with longtime collaborator Stephen McFeely. The duo has been with the MCU since 2011's Captain America: The First Avenger and also worked on Thor: The Dark World, Winter Soldier, and Civil War.