SHIELD May Have Broken The Time-Space Continuum In Season 5
But why would two different dimensions interact with one another like this, and why hasn't it happened before? The answer could be that S.H.I.E.L.D. broke the time-space continuum back in Agents of S.H.I.E.L.D. season 5. It's important to remember that, although links to the films have become a little more tenuous over time, the Marvel TV shows are all set in the MCU and the basic rules still apply. According to Doctor Strange, the time-space continuum is very fragile indeed. In one scene, Doctor Strange experimented with the Time Stone on an apple, to the horror of Wong and Mordo. "Temporal manipulations can create branches in time," Mordo warned furiously, "Unstable dimensional openings. Spatial paradoxes, time loops!" Wong agreed; "You weren't manipulating the space-time continuum, " he fumed. "You were breaking it."
Agents of S.H.I.E.L.D. season 5 was all about time travel. S.H.I.E.L.D. found themselves caught in a time loop, one that involved the destruction of the entire planet, and everything they did appeared to be predestined. However hard they tried to break the loop, the future seemed impossible to change, and Fitz even began to lose hope and believe the future was set in stone. In the end, of course, he was wrong; one single decision by Phil Coulson changed everything, when he chose to slip the Centipede Serum into Quake's gauntlet rather than use it himself. Her powers enhanced by the serum, Quake was able to beat Graviton and save the Earth, albeit dooming Coulson to die at last. The loop had been broken.
But what effect did this have on the time-space continuum? S.H.I.E.L.D. had essentially done just what Wong and Mordo cautioned Doctor Strange against; they had created a new branch in time, potentially damaging the time-space continuum. Over in the comics, this kind of action has been known to have devastating effects. The most dramatic example was in 2013's "Age of Ultron" event, when time shattered and fragmented. Realities merged, portals opened between alternate timelines, and living beings like Angela - Thor's long-lost sister - found themselves stranded in the normal Marvel dimension. It's possible S.H.I.E.L.D.'s act had a similar effect, although on a less dramatic scale. What's more, given it was Coulson who caused the damage, it'd be less surprising that an alternate version would got caught up in it all.
Is Agents of SHIELD Season 6 Exploring Alternate Dimensions?
Marvel comics have frequently used the idea of alternate dimensions to create "What If?" realities in which events played out very differently. What if Daredevil had killed the Kingpin? What if the Punisher's family had not been killed? What if Spider-Man's Uncle Ben had lived, and Aunt May was murdered instead? Oddly enough, many of these alt-universe adventures inspired ideas that were ultimately done in the main comics; Spider-Man really did join the Fantastic Four, Jane Foster became Thor for a while, and Reed and Sue Richards did have a second child, Valeria. The concept was faithfully reproduced on the big screen just last year, when a number of alt-universe Spider-Men worked together in Sony's animated Spider-Man: Into The Spider-Verse blockbuster.
Agents of S.H.I.E.L.D. season 4 already experimented with the idea a little, with Coulson and his team trapped in a virtual reality known as the Framework. In this world, Hydra had successfully conquered America; Coulson was a schoolteacher, Agent May was one of Hydra's top operatives, and Fitz was in a romantic relationship with Madame Hydra herself. But season 6 could go a lot further, with an alt-Coulson crossing paths with S.H.I.E.L.D. at a time when the pain of Coulson's loss is still fresh to May and her colleagues.
Of course, if there's an alt-Coulson, it stands to reason there may be doppelgangers of the other S.H.I.E.L.D. team members as well, which means almost every scene in the Agents of S.H.I.E.L.D. season 6 trailer should be viewed with real care; some scenes may well show duplicates in action rather than Mack's S.H.I.E.L.D. band.