Even 4 years after Avengers: Endgame changed the MCU forever, the crossover event movie continues to play a key part in Marvel's tent-pole franchise. Endgame's ending brought the curtain down on the first era of the MCU, retrospectively named the Infinity Saga, retiring both Robert Downey Jr's Tony Stark and Chris Evans' Captain America and breaking apart the first iteration of the Avengers team. It came as no surprise in the aftermath when the MCU struggled to put the events of Endgame behind it properly.

The MCU can't help but continue the Endgame story, even after the end of the Infinity Saga, ranging from the smaller details (like Thanos potentially being an Eternal and his "tragic" backstory not quite fitting) through to qualifications of how Captain Marvel was able to over-power Thanos. As the Mad Titan remains such an intriguing presence in the MCU, it's no surprise that Doctor Strange in the Multiverse of Madness also offered a reason why Scarlet Witch couldn't beat him, despite her power levels: she hadn't unlocked her potential using the Darkhold. It's fair to say that Endgame is effectively a core canon event in the MCU, and a fulcrum on which lots of other stories depended, including almost all of Phase 4.

Each of the following Marvel releases substantially changed details from Endgame years later:

• Black Widow
• Doctor Strange in the Multiverse of Madness
• She-Hulk
• Falcon & The Winter Soldier
• Ms. Marvel
• Secret Invasion

9 Doctor Strange 2 Proved There Was More Than "One Way" To Beat Thanos

Iron Man's death at the end of Endgame was a heart-stopping moment made all the more devastating by its inevitability: Benedict Cumberbatch's Doctor Strange had promised that there was only one way Thanos could be taken down after scouring millions of timelines and possibilities. Ultimately, it all came down to Iron Man sacrificing himself, making his death even more noble. Except it didn't last. In Doctor Strange in the Multiverse of Madness, it was revealed that The Illuminati killed Thanos in Earth-838's timeline a completely different way. The reality became clear that Strange was misinformed, and his own sequel went further, establishing the idea that fated outcomes could be challenged when he refused to sacrifice America Chavez to save the universe once more. In essence, there absolutely was not just one way for the Avengers to win and shockingly, it seemed Iron Man possibly didn't have to die.

8 Smart Hulk Isn't Permanent, Actually

Of all of the MCU's post-credits scenes, Shang-Chi's credits scene caused the most confusion. Avengers: Endgame had established that Bruce Banner had permanently found balance between his Banner and Hulk identities by arriving in the middle with Smart Hulk (sometimes known as Professor Hulk), marrying Big Green's brawn with the Science Bro's brain. It was an inelegant solution, since it still erased Hulk and exacerbated the idea of Banner using his body, but it still worked as a resolution to the character's internal conflict all the same. But then Shang-Chi's post-credits scene showed Banner in his puny human form, complete with his Endgame injury, raising a pretty big question.

In a rare move, Kevin Feige actually explained this one - or at least the reason why Banner's human form was always going to return in the MCU. As The Story of Marvel Studios: The Making of the Marvel Cinematic Universe book, explained: '"We never even considered doing Planet Hulk because, as cool as we thought the comic was, Bruce Banner is not a part of Planet Hulk." And Banner has always been an important component of the Hulk storytelling the studio wants to explore.'

It wasn't until She-Hulk arrived in the MCU that the retcon was explained, when Bruce reveals to Tatiana Maslany's Jen Walters that he invented a special Hulk Inhibitor Device, to allow him to transform back to his human form. On top of that, She-Hulk reveals Banner has developed a personal program for managing Hulk, including yoga, mindfulness meditation, and even dialectical behavioral therapy. Once again, Hulk became a problem for Banner to manage, rather than a thing to be harmoniously balanced, as he had done in Endgame.

Related: Why Is Bruce Banner Is No Longer Hulk In Shang-Chi

7 Secret Invasion Added Endgame's Missing Post-Credits Scene

Unlike most MCU movies, Avengers: Endgame has no post-credits scene, and rightly so, as the Russos avoided undermining the importance of the ending by immediately looking to what would come next. But 4 years later, Secret Invasion added the post-credits story Endgame couldn't show, revealing Nick Fury sent a Skrull extraction team led by Kingsley Ben-Adir's Gravik into the battle arena to steal samples of the Avengers and Thanos' army, including the Mad Titan himself. The DNA serum created from that mission included most of the super-powered heroes, including Captain Marvel, Hulk, Drax, and both Captain America and Bucky among others. That revelation also added a different tone to the fact that Fury turned up to Tony Stark's funeral, suggesting he was attending to secret business as well as mourning a supposed friend and colleague.

6 Phase 4 Fixed Avengers: Endgame's Bucky Crime

The Falcon and the Winter Soldier's penultimate episode, "Truth" finally fixed the issue with Captain America's Endgame farewell, revealing a key moment between him and Bucky that was never actually shown on screen. Endgame had already caused an issue by not having Steve share his plan to stay in the past with Peggy, despite their close relationship. The Falcon and the Winter Soldier episode 5 belatedly had Bucky reveal that Steve and the former Winter Soldier actually did talk about his plan: "When Steve told me what he was planning, I don't think either of us understood what it felt like for a Black man to be handed the shield. How could we? I owe you an apology. I'm sorry." That final interaction being added retrospectively, and giving Bucky both his missing goodbye and likely informing him of Steve's plans to return to Peggy was a huge deal.

Related: Marvel Retconned Avengers: Endgame's Biggest Captain America/Bucky Problem

5 Secret Invasion Confirmed 2 Missing Endgame Heroes In The Final Battle

Despite releasing as part of the Multiverse Saga, Marvel's Secret Invasion was an Endgame epilogue, exploring not only the impact of the blip on Samuel L Jackson's Nick Fury, but also establishing how the Blip and his subsequent absence from Earth led to the Skrull uprising under Gravik. Central to the entire Secret Invasion plot was the reveal that Fury ordered the Harvest of Avengers DNA (as well as other super-powered individuals) with the grand reveal showing every character included in the Avengers DNA on a computer screen. That list included both Abomination (Tim Roth) and Ghost (Hannah John-Kamen) who previously only appeared in Ant-Man & The Wasp. Neither of those characters were shown in Endgame's final battle, but Secret Invasion retroactively added them to the mix.

4 Ms Marvel Contradicted Endgame's Time Travel Rules

Avengers: Endgame went to great lengths to explain how time travel was possible, establishing rules through Bruce Banner that would both confirm it was scientifically possible but also closing the loophole that it could just be used forever in the MCU to solve every issue. Smart Hulk's explanation established the limits of time travel: “If you travel to the past, that past becomes your future, and your former present becomes the past, which can't now be changed by your new future.” Essentially, it would be impossible to go back in time to change your own present, as it would instead create branched universes, which is why the Avengers couldn't simply go back in time and kill Thanos.

3 years later, Ms Marvel broke that Smart Hulk's time travel rules. In episode 5, "Time and Again" Kamala Khan (Iman Vellani) goes back in time to the night her great-grandmother, Aisha (Mehwish Hayat) disappeared during the Partition of India and is able to interact with her family. At Aisha's bidding, Kamala helps the lost young Sana (Zion Usman) reunite with her father, explaining a story from an earlier episode. That interaction didn't create a branched reality, because the changed past didn't become Kamala's future and she was able to return to her own time that followed on from Sana's rescue at the train station.

3 Black Widow's Backstory Changed Her Best Endgame Speech

In Avengers: Endgame, Black Widow reveals the personal tragedy of the Blip "killing" several of her hero friends, as well as explaining why she remained an active hero: "I used to have nothing. Then I got this. This job... this family. And I was... I was better because of it." The implication was that the Avengers stopped her being lonely, disconnected and emotionally unavailable: they changed her life because they accepted her into the found family dynamic, no matter how dysfunctional it was at times. But then Black Widow revealed that Natasha had an actual family in her early life - albeit one forced together by the Red Room. She grew up for a while in the care of Red Guardian/Alexei Shostakov, and Melina Vostokoff with her sister Yelena Belova, who the movie established were a genuine family to her, and retconning the idea that she'd always had nothing.

Related: Black Widow's Russian Family Is An Avengers: Endgame Retcon

2 Ms Marvel Confirmed SHIELD Joined The Endgame Final Battle

Ms Marvel changed the idea of the Avengers in the MCU by giving them a fandom. At AvengerCon, in-universe fans including Kamala Khan could celebrate their heroes (including the Guardians of the Galaxy) and buy merch. As well as revealing that the world knew the most intricate details of Endgame's Battle of Earth thanks to Ant-Man's podcast (called "Big Me Little Me, A Scott Lang Interview") the convention also revealed that SHIELD agents participated in the battle. Hidden in the background of the AvengerCon scenes, a standee advertized a book called "I Was There", which remained a mystery until Marvel.com confirmed it was written by a SHIELD agent on the ground (6000 ft from where Tony Stark died) detailing “the clash between the heroes of earth and the Alien scourge threatening our fragile planet.” This was the first hint at all that any of SHIELD's personnel actually turned up for the battle.

Related: Every Hidden Detail & Easter Egg In Ms Marvel's AvengerCon

1 James Rhodes Was A Skrull During Avengers: Endgame

Perhaps the most difficult Avengers: Endgame retcon to accept came in Secret Invasion when it was revealed that James Rhodes had been a Skrull since Civil War. Fans immediately took to social media to scrutinize the reveal, suggesting why it was a bad idea and why it couldn't possibly make sense, despite director Ali Selim making it clear that was the thinking behind the real Rhodey wearing a hospital gown during his rescue in the finale. Most disturbingly, that meant that Rhodey was a Skrull during the final Battle of Earth, and for his tender moment consoling Tony Stark as he lay dying (the first character to actually do so). That was a horrible way to undermine the moment between two long-term friends, and it's no surprise there have been calls for Armor Wars to establish that Rhodey was replaced after Endgame as a result.

The 1 Endgame Retcon Kevin Feige Refused To Allow

Despite all of the changes the MCU has so gleefully made to Endgame since its release in 2019, one proposed change was actually stopped by Marvel supremo Kevin Feige himself. As revealed by Ms. Marvel executive producer and head writer Bisha K. Ali, Feige vetoed one Endgame retcon proposed for Ms Marvel, which would have added some Endgame footage to Kamala Khan's monologue about why she loved Ms Marvel so much. The catch, though, was that it would reveal that the footage was captured by drones from a Twitch streamer live broadcasting the battle to the world:

At one point, like early days before we kind of expanded the creative team out, I was like, "Kevin, what if there was like, drones and a live stream of the battle of Endgame?” And he like, "Bisha, no," I’m like, there wasn’t one Twitch streamer around for the final battle of Endgame? Are we kidding? I think I lost my mind at that point, try to solve this riddle. So it was really a big iterative journey.

Let's all be thankful Kevin Feige drew the line there and protected Avengers: Endgame in at least this case. That led to Ms Marvel introducing Ant-Man's podcast and giving Scott Lang some of the adulation his character hadn't enjoyed prior to Endgame's events. Considering he was so key to saving the universe, that was a way more fitting way to explain the world's knowledge of the Battle of Earth than giving credit to a random Twitch streamer.