Epileptic Trees / Avengers: Endgame

• The title itself, given the secrecy behind it, was the subject of a lot of speculation. Popular candidates for the movie's name included Avengers: The Infinity Gauntlet,^note which was Jossed shortly after the release of Infinity War Avengers: Infinity Crusade, ^note the name of the sequel to the original Infinity War comic Avengers: Secret Wars,^note which the directors heavily implied was not the case when they mentioned a desire to adapt such a story in case Disney acquires Fox Avengers: Secret Invasion, Avengers Disassembled, Avengers Forever, ^note which the directors stated was the closest guess to what the actual title was, considering that Avengers Endgame was an actual guess at the time, however, this appears to have been misdirection in hindsight Avengers: Annihilation, and, naturally, Avengers: Endgame.^note Ironically implied not to be the case at the time because the directors stated that the title of the fourth Avengers movie was not spoken in Infinity War... which, of course, later turned out to actually be false.
• The set photos showing an older Tony Stark and Scott Lang interacting with Steve Rogers as he appeared in The Avengers, along with some other set photos showing characters in costumes that they wore earlier in the continuity, led to the theory that Avengers 4 is a movie based around Time Travel. Adding to this is that Kevin Feige mentioned that the Grand Finale of Star Trek: The Next Generation ("All Good Things..."), which prominently featured characters jumping through time, was a key influence on this story, along with set photos showing Scott interacting with Gamora and Nebula as they appeared in Guardians of the Galaxy (2014). Of course, Endgame did turn out to be a Time Travel movie.
• The fact that (A) Clint returned as Ronin rather than Hawkeye, his future Disney Plus show was announced involving him training Kate Bishop, and the fact that Clint begins the movie training with his daughter; (B) a casting call was leaked for baby twin boys who are believed be those of Scarlet and Vision; (C) Patriot was originally planned to appear in Black Panther before being cut due to the large cast; and (D) Cassie Lang has been aged up to a teenager (in line with her comics counterpart) has a number of people suspecting that a Young Avengers movie is being set up by the MCU for Phase 4, starting from here. Like the Guardians of the Galaxy, they wouldn't exactly be expected compared to other big names with longer histories, seeing as they were only introduced in 2005. After the movie's actual release, the debut of Morgan Stark and the return of Harley Keener have added fuel to the fire.
• Then there's the confirmation that Phase 4 will include LGBTQ characters which added even more speculation — Wiccan and Hulkling are among the most well-known of Marvel's gay superheroes. And the fact that Phase 4 will introduce more Legacy Characters, again fitting with the theme of Young Avengers. And then Feige outright stated that Cassie was introduced as a child in the Ant-Man movies to "plant seeds" for the future. By this point, Young Avengers fans are really hoping for there to finally be a young superhero team movie that's never been made before.
• There's also the theory that the day that Marvel took the "class photo" was the day that they filmed the big sequence with forty characters that has been confirmed to appear in this film. The actual movie casts a very dark shadow over this, as the only scene that most likely involved all these actors, without having to green-screen them together like a Big Badass Battle Sequence would need, is the funeral of Tony Stark.
• As his actor was allegedly been spotted on set, the acquisition of Fox by Disney granting Marvel the X-Men film rights, and the theories that the movie will involve time travel, many believe that Pietro Maximoff/Quicksilver will be brought back to the MCU after his death in Avengers: Age of Ultron. Sadly, this turned out to not be the case, though given that the movie involved Time Travel, this would not have been a bad guess if one of the places the Avengers returned to were the Battle of Sokovia.
• Some believe that the franchise's new status quo will revolve around an older Cassie Lang rebuilding the world years in the future, with any reversals to Thanos wiping out half of the universe's life being fairly minor. It turned out to be incorrect, but the movie does keep an older Cassie Lang around that leaves her role in future movies open for exploration.
• A contingent also suspect that with the reshoots taking place, and neither it nor any concept art seen so far showing anything past-related, that the idea of Time Travel being part of the plot was a smokescreen intentionally made to fool the audience and cover the real plot of the movie, the bulk of which filmed in reshoots rather than the original photography. Adding to the theory, Word of God confirms they've filmed fake scenes specifically to provide fake spoilers and keep the film under wraps.
• The fact that Clint will be appearing not as Hawkeye but as Ronin has led many fans to assume that his wife and kids were killed in the Snapture. This is confirmed in the opening scene of the film.
• After Chris Evans posted this on Twitter, the theory that Captain America is going to be Killed Off for Real spread like wildfire. When it came to deadpools Cap would be at the top of majority of them. Although he comes this close to biting the dust, this turned out to be misdirection, even though Cap's story more or less ends with this film.
• The first official trailer showing that Tony and Nebula were trapped, adrift in space in the Guardians' spaceship, the Benatar, had prompted some suggestion that they'd be rescued by Kraglin. Others have theorized they'd instead be picked up by Korg, Miek, and Valkyrie (along with any Asgardian survivors). They are ultimately rescued by Carol in the film.
• A leaked photo suggested Pepper would be suiting up as Rescue. She does.
• Some speculated that Drax's dusting would be permanent due to Dave Bautista's objection to the firing of James Gunn and publicly expressed his doubt for returning for Guardians of the Galaxy Vol. 3, before the latter was re-hired. This ended up being Jossed as Drax ends up living.
• 2012 Loki escaping with the Tesseract and never appearing again provoked some suspicion that rather than being a prequel, his series on Disney+ would about this Loki's adventures on the run. They were right, though probably didn't foresee the TVA.
• Quite a few people guessed the briefly mentioned underwater earthquake is foreshadowing for Namor the Sub-Mariner. While the writers stated that the earthquake was not intended to be related to Namor, he did in fact turn out to be the main antagonist in Black Panther: Wakanda Forever.
• With time-travel being a key factor in the movie, a lot of fans began speculating that Kang the Conqueror may play a role in Phase 4. Some fans even theorise that due to Tony Stark being the first to successfully pioneer time-travel, Tony Stark may be Kang's ancestor in this continuity as opposed to Reed Richards or Doctor Doom in the comics. For the former case, the confirmation that Kang will appear in the sequel to Ant-Man and the Wasp after first appearing in the Loki show has added more credence.
• There are a few people who think the homosexual man in Cap’s support group is the MCU version of Arnie Roth — a gay man who was Steve’s best friend and pre-serum protector in the comics.
• Some fans like to believe that a few of the non OST tracks heard in this film (i.e: "Supersonic Rocket Ship" by The Kinks, "Hey Lawdy Mama" by Steppenwolf, and "Doom and Gloom" by The Rolling Stones) are songs from Peter Quill's Zune, due to them all being artists from the seventies.
• In another one from people impatient to get the X-Men and Fantastic Four in the MCU, several people started insisting that Captain Marvel telepathically tells Thor "I have telepathy" when he summons Stormbreaker past her head, thanks to some random weird voices in the soundtrack.
• Due to the Broken Base over Steve's actions and how a good portion of the fanbase saw it was vehemently Out of Character, a fair number of them tried to resolve the contradiction by claiming that the Steve Rogers at the end of the film was actually a Skrull imposter, bolstered by statements that the MCU were planning to adapt Secret Invasion.