Avengers: Endgame - Everything That Changes If The Heroes Steal The Infinity Stones From The Past

There's a fairly big suggestion that Avengers: Endgame is going to include time travel as they key (or part of the key) to undoing Thanos' Decimation of the universe. You already know this, not least because of the number of theories that are out there (and partly thanks to Samuel L Jackson's liberal application of "accidental" Captain Marvel spoilers).

Whether it comes down to the Quantum Realm, Captain Marvel's powers, a trick of the Time Stone or something else entirely, though, it goes without saying that time travel is a tricky thing to start messing with. Many a blockbuster has fallen into the trap of pulling out a time machine or a cheeky time portal to "fix" the plot only for gaping plotholes to rip like trenches through them. Even some of the most celebrated time travel movies of all time - Back To The Future, Terminator, Interstellar - have messed up.

The key for Avengers: Endgame - particularly if the pervading theory on WHY the heroes time travel is true - is that they have to really consider the butterfly effect. If, as suggested, the Avengers go back to retrieve the Stones before Thanos can get his hands on them, we're going to see some key events and entire characters from the MCU wiped out entirely. That's if they're not incredibly careful about WHERE they steal the Stones from in the timeline.

Presumably, the safest choice would be to go and steal them from long before Thanos was on their trail, but that's the big problem. If the Avengers do that, we're going to see reverberations in the MCU that would change absolutely everything...

13. Red Skull Remains Active, Cap Stays In The '40s

Even without his obsession with the Infinity Stones, Red Skull would still have been a threat to the world back in the 1940s. In actual fact, he would probably have been a more dangerous one, free to concentrate more on global dominion rather than an obsessive focus that bottle-necks his attention away from the Third Reich's plans.

If the Avengers were to steal the Tesseract from its hiding place in Tønsberg, where Odin left it when he brought it to Earth, Red Skull may never have exhaustively sought it at all, though it still seems likely he would have been intoxicated by its mythology.

What is more tangible as a result of the Tesseract being taken at that point is that Red Skull would not have come into contact with the cube, would not have touched it with his bare hands and would not have been teleported to Vormir. He would, most likely, have continued to seek ways to "improve" himself and most importantly, Captain America would not have been drawn into the specific conflict with him that led to him sacrificing himself, being frozen and waking up in the future.

That's a fairly big reason to not steal the Tesseract too early.