'Avengers: Endgame' Writers Explain How 'Harry Potter' Influenced Their Rules on Time Travel

Following the devastating conclusion of Avengers: Infinity War, all eyes were on Avengers: Endgame and its creators to develop a satisfying way to reclaim the Infinity Stones and resurrect the fallen heroes. This week, the film’s writers explained part of their creative process in developing this plot device, offering one unexpected influence: the Harry Potter series.

In the film, the surviving Avengers use Ant-Man’s Quantum Realm technology to travel back in time and acquire the past versions of the Infinity Stones, meaning that screenwriters Christopher Markus and Stephen McFeely had to develop their own time travel rules. Per ComicBook.com, Markus and McFeely researched time travel films including Back to the Future, but ultimately concluded that its rules would not fit.

“Everyone thinks that how time travel works because that's a great movie, maybe the best of its subject,” McFeely said. “But if we were to do that, to do something in the past and it would screw up your future, we're gonna do that six times. We would have no way to follow that.”

Instead, they drew inspiration from the rules of Harry Potter and the Prisoner of Azkaban, which includes a time travel mechanic in the form of the time turners. "I do love that, say, third Harry Potter movie, where [we see] a stone break a vase. You don't know why, but the scene's fine and it doesn't take you out of it," McFeely explained. "Then when you come back around [during the time travel sequence] and you realize that they had thrown it at themselves, I do love that."

Like Prisoner of Azkaban, Endgame sees its protagonists actively interacting with the past, with some characters even meeting their past selves, and paradoxes from the time travel sequence, such as Thanos’ past self dying in the future, being left unresolved.

Although we could certainly delve into Endgame’s deep time travel lore all day, we’ll stop ourselves here and say that we’re glad that Markus and McFeely developed the film in a Harry Potter-inspired vein--it was a huge part of making it as special as it is.

This article also appears on Mental Floss.