The Odinson clan have a hard time keeping their eyes in their skulls - Odin lost one of his eyes a long time ago (but got a very snazzy strapless gold eyepatch) and there was about an 18 hour time period where Thor was down an eye, thanks to a real inopportune gouging by his long-lost sister Hela. But - if Thor had just been paying attention to the symbolic foreshadowing that lay in front of him, he may have seen that coming.
See, when Hela returns to Asgard, she's none too happy about a few things - namely, that her existence has been erased from the histories, even the giant family mural that stood in the throne room. So, she tears it down...revealing an older, more Hela-centric mural:
Honestly, it was kinda weird they didn't just paint over the original mural? Like, instead of building a new ceiling right on top of the old one? Whatever, I'm not going to question Asgardian architectural choices. But back to that second, now-destroyed mural - the way it falls on the ground reveals a very interesting crack...across the eye that a certain Asgardian is about to get removed (and a nasty scar left behind):
Also, some have noticed that there was some RETROACTIVE foreshadowing going on in Thor 1 (otherwise known as a "coincidence that doesn't actually mean anything"):
At the start of Captain America: The First Avenger, Johann Shmidt (yes, it's spelled that way) rolls into a Norwegian church, TOTALLY disrespects character actor David Bradley, and takes the Tesseract (aka the Space Stone). And he does it all without revealing there was anything too weird about him - just a normal occult-obsessed Nazi stealing glow-cubes from old men in Viking churches. The nerds out there knew it was coming, but for most the reveal that Johann Shmidt's true appearance is that of an ACTUAL RED SKULL was a pretty big twist:
But as you can see from the first image up there, the signs that Red Skull was wearing a skin-mask were there from the start. Although - really - everyone should know by now that if you cross Walder Frey, you wind up covered in red.
Okay, so technically there is no character referred to as "Mary Jane" in Spider-Man: Homecoming, but in her place in Michelle Jones - also known as MJ - the sarcastic, observant slacker who perpetually hangs around the edges of the film 'til the end, where we realize that Liz isn't the love interest destined to capture Peter Parker's heart: Michelle is. She doesn't have the red hair or Mary Jane's semi-bland generic love interest personality, which is all the better to distinguish herself from the Kirsten Dunst iteration of the character.
But while some things can change about MJ and it not be a big deal, one thing has to be included: her referring to Peter as "tiger," and preferably telling him to "go get 'em, tiger."
Sadly, she doesn't say that - but the phrase DOES make its way into the film anyways, by means of making the school's team name "The Tigers":
Now all Michelle needs to do is get unholy amounts of plastic surgery to warp her body proportions and allow her to contort her body in some classic MJ poses:
The ending of the first Thor film should be a pretty consequential moment - Thor chooses to destroy the Rainbow Bridge rather than risk the fate of Jotunheim, home of the Frost Giants. This cuts him - and all of Asgard - off from the remaining Nine Realms, including Midgard, where Thor's hot new scientist girlfriend happened to live. It's a big decision to make, but Thor - having learned sacrifice and humility - chooses to make it, because it is what was necessary in the moment.
And with that, his path to Midgard is cut off...until the VERY next film, The Avengers, where Thor is totally able to get back to Midgard, easy peasy. Loki makes an offhand reference to Odin gathering a bunch of "dark energy" to be able to send him there, but it's all just gibberish because the MCU wasn't as good with meaningful continuity back then. However, they do sorta make up for that in Thor: The Dark World - when the Dark Elves begin their invasion of Asgard, good ol' Heimdall goes running to take down the scout ship before it gets too far. As he's running down the (repaired) Rainbow Bridge, we can very clearly see the spot where Thor smashed it to bits previously:
Honestly, a pretty crummy job. Doesn't really fit in with the rest of the bridge at all, although maybe this was just a first pass and they were gonna make it all nice later on? Actually, I kinda hope not - given the events of Ragnarok, it wouldn't have had much of a point.
Skurge's introduction in Thor: Ragnarok is pretty great - he's bragging about all the cool stuff he's collected as the new Heimdall (since the old Heimdall got fired by Loki-Odin and they needed someone with looser morals to man the Bifrost) to two women, who look mildly bemused (and probably wondering a bit what ever happened to Lady Sif):
Of course, the brag-session was cut short by Thor's return, and the bloody dragon head he brought along with him:
After this, things start going bad for Asgard: Odin is revealed to be Loki in disguise (and the REAL Odin is missing, leaving the rest of the Nine Realms unprotected), Hela returns and murders pretty much everyone except Heimdall and Lady Sif, the few remaining Asgardians hide out, and eventually they all come together to fight alongside Thor in a desperate last battle against Hela and her forces.
Including the traitorous Skurge, who turned on his fellow Asgardians to become Hela's executioner. Naturally, the remaining Asgardians weren't too big of fans of his after this, so when he finally came face-to-face with his compatriots again, they decided to charge straight into him...and they were led by none other than the same two ladies he was trying to impress at the beginning of the film:
Of course, eventually Skurge has a change of heart and goes out, guns blazin' - as all Karl Urban characters should.
The final confrontation between a broken, beaten-down Ultron drone and Vision is one of the true saving graces of the otherwise sorta meh Age of Ultron - a quiet, oddly serene, beautifully-shot scene between two AI beings with incredibly different viewpoints. It's after all the action, but is both strangely hopeful and deeply pessimistic. And "Well, I was born yesterday." is such a delightful line.
But that busted-up final Ultron drone should look familiar - because it's the same one Cap kicked off the flying city early in the battle.
If you look closely, you notice the same Captain America's shield-sized gash from the Ultron drone's right shoulder and across its torso - that, and it's one of the few Ultron drones that wasn't COMPLETELY obliterated that was also tossed off the city as it rose into the sky:
Also, this brings up another good point: WHY DOES CAP NEVER USE THOSE COOL MAGNET GAUNTLETS HE HAS IN AGE OF ULTRON? Those things kicked ass.
Most of Tony Stark's bright ideas don't pan out so well - ignoring Guy Pearce led to Extremis, trying to protect the world with Ultron led to nearly DESTROYING the world with Ultron, and then there was that whole "being on the wrong side" of the Civil War debacle. This isn't too off from his comics counterpart, who has all the same gusto and arrogance as the MCU Tony Stark, plus a lot more problems with addiction (and occasionally being dead, sorta). But one major mess-up that MCU Tony hasn't yet delved into is...the Illuminati.
Formed as an extranational shadow organization, Stark, Charles Xavier, Black Bolt, Namor, Dr. Strange, and Mr. Fantastic all gathered together to try to solve the world's problems before they started. They were all great minds, all powerful, and all deeply influential in various communities - the perfect individuals to find the solutions that governments and other organizations weren't able or willing to see. And naturally, it led to practically nothing but an endless series of screw-ups. One of the biggest, of course, being exiling Hulk from Earth via spaceship, against his will - and stranding him on an alien planet (Hulk was a little pissed off about that whole thing, eventually leading to World War Hulk).
And - in Iron Man 2 - when Stark is toying around on his phone during the court room sequence early on, we see an item on his phone labeled "ILLUMINATI." Maybe it was a little joke Stark had cooked up - or maybe it was a hint that there's been a secret organization going on in the shadows of the MCU this whole time, and Marvel Studios has also gotten the rights to Mr. Fantastic, Professor X, and Namor back. Stranger things have happened.