Avengers: Endgame (2019)
- He mentions Star Trek, whose time travel theory is actually very similar to this movie. When Spock Prime traveled to the past, all the changes made did nothing to affect his own timeline, however he still sought to make sure that the newly created timeline remained somewhat similar to his own.
- He then mentions three - The Terminator, Somewhere in Time, and Bill & Ted's Excellent Adventure - which follow the theory of the Feedback Loop or Predestination Paradox, which states that anything done by a time traveler to change the past ironically causes the future to unfold the way it has always done.
A Quinjet travels to Tokyo, where Ronin (Hawkeye) battles Akihiko, a Yakuza.
During the sword fight, the camera pans around the combatants; we see a cut visible under Akihiko's left cheek.
The fight continues, and the camera pans again; this time, the cut has disappeared.
Errors in geography
Incorrectly regarded as goofs
Thanos presumptuously believed that everyone would be grateful that he "saved the universe", which is made clear when he tell the Avengers that they "should be grateful" that he murdered trillions. Perhaps he expected everyone to express their gratitude by cutting down on reproduction in order to maintain balance.
However, in this particular shot, the camera is on the opposite side of the hologram from Thanos. Thanos would be looking at the holographic reflection of Nebula, which is a mirror image, but the camera is on the opposite side and would pick up the flipped image.
However, just because this is how the editing timed out like this in this movie, that doesn't mean that it happened in "real time" - it was most likely a jump cut from the 2012 Avengers team-up shot to the present-day Avengers to show up in 2012.
Incorrectly regarded as goofs
But for almost every stone, it's going to be difficult, if not impossible, to return it without anyone seeing the difference - some stones were stored in containers that were broken, others were in artifacts that were destroyed to get to the stones.
Further, when Steve Rogers goes to return them, we very specifically see him with ONLY the stones, and not their original artifacts, or any way to repair the containers.
Apparently Steve must only deliver the stones to the moment they were taken from the past. Because as the Ancient One explained, the stones create the flow of time and removing one of the stones causes that flow to split. So Cap didn't have to (let's say) put the Aether back into Jane. As long as the Aether (reality stone) exists in that timeline, that's enough for the timeline not to split.
The Russos confirmed the fact that Steve did indeed live in an alternate timeline - but how he made it back was intended to remain a mystery for now.
However, recall from that same scene is Ant-Man and the Wasp, Janet warns Scott to not get sucked up into a time vortex. After the time skip, where he evidently traveled through a time vortex, Scott mentions that the quantum realm is chaotic and unpredictable, and thus pitched the idea of "controlling the chaos" to make a time machine - clearly this shows that the 5 hours of quantum time wasn't directly proportional to the 5 years of real time that passed.
The population is more than doubled, since some births would have occurred in the intervening 5 years. They'd live at the same places, that they had five years ago. When Scott Lang makes it out of the quantum realm, he walks past rows of empty houses.
As for food, when the snap is undone, Scott sees birds suddenly appearing, suggesting that the snap extended to animals as well, which would now have doubled (supplying people with more to eat). fields on farms could be replanted, since with fewer people to feed, the fields would've been left to fallow. In Infinity War, Thanos notes that Gamora's planet had a surplus of food and resources, after he wiped out half of the population. Applying it to Earth, the world would've had a surplus of food, for the last five years. At worst, society would have to institute ration cards (as many countries did during the world wars), until more food can be produced.
In previous films (more particularly Guardians of the Galaxy), it is established that only direct bodily contact with an infinity stone will cause that person to be destroyed, unless that person is a species that could withstand it (such as a Kree, Celestial, Titan, etc.). It's also established that any kind of weapon or gauntlet would allow the wielder to use the power of the stone(s). This being the case, Tony attaching the stones to his Iron Man gauntlet would have allowed him to use the stones (although still having a huge amount of energy flowing through him), but it is perfectly accurate that the energy was enough to kill him when he snapped his fingers.
Previous movies with Ant-Man seem to suggest that the Ant-Man suit somehow has a permanently charged Pym particle, as he can shrink and grow at will. If not that, it is perfectly conceivable that it wouldn't require an entire canister of Pym particles for basic shrinking and growing, but it would require that much for quantum travel.
As of the Benatar, Ant-Man most likely had some shrinking and growth disks left over from his previous adventures with the Pym family, so it's most likely that he would have used a shrink disk on the Benatar and then gave Clint and Nat some more shrink and growth disks so that they could operate the Benatar in 2014 and then shrink it again for when they returned.
However, just because that theoretically could work, it wouldn't be the most ethical thing to do. The Ancient One mentioned that, although stealing an infinity stone would benefit the timeline of whoever took it, it would destroy the timeline from whence the stone was stolen. Bruce Banner was courteous enough to suggest the idea of returning the stones to exactly the moments from whence they were stolen in order to prevent those other timelines from splitting. Even though Captain America did successfully return the stones to those moments, that didn't change the fact that they still did a lot to undesirably change those timelines in the process of stealing the stones (more particularly 2012 Loki escaping with the Tesseract, or 2014 Thanos discovering 2023 Nebula and then traveling to her timeline). This being the case, if the Avengers used time travel to revive Vision, they would bring the mind stone with them and thus destroy whatever timeline they stole him from. As of the case of Black Widow and Iron Man, bringing them back wouldn't destroy those timelines, but it would drastically alter the fates of those timelines in which their crucial sacrifices to undo Thanos' actions wouldn't happen. Plus, they probably would have refused to be stolen from their timelines.
Strange is established as having seen the future and is attempting to ensure that they'll have the one future (out of over 14 million possible futures) where they win. The characters who were not there were not summoned, because Strange had not seen them there. They might have been there in some of the possible futures, where the heroes lost. Which would give Strange a motivation to not summon them.
It is also possible that some of those characters were actually present at the battle; we just didn't see them. After all, we saw dozens of portals open, some only from a distance.
In Avengers: Infinity War, Tony speculates that Pepper might already be pregnant. In Iron Man 3, we see them sleeping in the same bed (suggesting that they're already sexually active with each other). A pregnancy bump starts to show somewhere between 12 to 16 weeks, for first-time moms. So, Pepper could have already been pregnant for months (just have not informed Tony, yet), before Tony left Earth.
Recall that Strange had foreseen 14,000,605 possible endings for the war against Thanos, with this movie's ending being the only possible way for Thanos to have been defeated. Strange inevitably knew about Wakanda because he already foresaw Thanos entering Wakanda to obtain the last stone and then snapping his fingers. In addition, since the snap was a universe-wide effect, the Time stone would have also shown Strange every single person across the universe who could have had a potential threat against Thanos (like Ant-Man, who provided the means to travel back in time and obtain the stones to snap everyone back into existence). This being the case, there is no possible way that Strange could have NOT known about everyone who showed up to battle at the end of the movie.
Using the Gauntlet would kill a MORTAL wielder, as we see on Tony Stark. However, we see Professor Hulk, a mortal merely 'upgraded' by gamma radiation snapping with it and surviving it. Therefore we can safely assume that more advanced being could use it, like Thor, or Carol, who actually grabs it in the climax.