During the finale of the series Russo Bros. Pizza Film School, Joe and Anthony Russo were joined by Back to The Future screenwriter Bob Gale as well as Stephen McFeely and Christopher Markus, who penned the script for Avengers: Endgame. The hour-long discussion shed a great deal of light on the themes of time travel rules that connected the two blockbusters, which also necessitated name-dropping Back to the Future in the superhero ensemble feature.
"One of the things that I'm really proud of is that we were able to explain time travel in a way that even a nine-year-old can understand it. That scene in Avengers: Endgame where they're sitting around and talking about time travel, I understand that when they first previewed the movie, [it] didn't have that scene in it. I was told that in the focus groups, people said, 'Well, wait a minute, in Back to the Future they could do this and they could do that.' And the filmmakers realized, 'Oh damn, we gotta deal with that, because everybody's knowledge of time travel, today, in 2019, comes from those movies. So they had to put that scene where Ant-Man says, 'What do you mean? Back to the Future's bullsh**?'"
But as Bob Gale pointed out, despite Avengers: Endgame attempting to distance its own rules of time travel from Back to the Future, the heroes ended up pretty much treading the exact same path in their own story as Doc and Marty.
"You say [in the movie] 'You mean Back to the Future's bullsh**?' And at the end of the day, you guys end up going back into the first Avengers movie and into the earlier Thor movies, so it really is kind of like Back to the Future."
As Joe Russo clarified, Ant-Man's disparaging remark regarding Back to the Future was not meant to be disrespectful, but rather an acknowledgment of the immense shadow cast by the movie on every other time travel film that came after it.
"If you're gonna try to get an audience to understand that you want to alter time travel rules. That's why we literally had to invoke Back to the Future in the movie at several points, so that we could say to people, 'Alright, these are different rules than Back to the Future.'"
Time travel is one aspect of sci-fi that writers generally try to avoid because it opens the storyline up to pesky paradoxes, and the persistent question as to why every fresh threat is not dealt with by going back in time and eliminating the factors that lead to the creation of the threat in the first place? For better or for worse, the MCU has now opened itself up to that particular can of worms, as well as the introduction of the Multiverse in the upcoming Doctor Strange in the Multiverse of Madness, meaning the world of the Avengers is going to be an extremely confusing place in the coming days.