At the time of The Avengers' release, Life Model Decoys was a deep cut reference to Marvel Comics by writer/director Joss Whedon. The robotic doubles were first introduced by Stan Lee and Jack Kirby in Strange Tales #135 back in 1965.
Our first look at the World Security Council is seen in the film, and most of the members would go on to reprise their roles in Captain America: The Winter Soldier!
Tony's homework about his fellow Avengers features a number of clips from the preceding films in the MCU.
The mysterious figure that appears throughout the film speaking to Loki, and later Thanos, is played by frequent Joss Whedon collaborator Alexis Denisoff. Denisoff previously appeared in Whedon's TV series Buffy the Vampire Slayer and its spin-off, Angel.
Barely visible to the naked eye, but when Thor attempts to extract Loki from SHIELD's possession, Odin's two ravens can be seen (and heard) in the background watching the events unfold.
Though we can't repeat the expletive uttered here, it's just worth pointing out that Joss Whedon was able to put a very X-Rated profanity in The Avengers (a Disney movie!) by dressing it in very Shakespearean terms.
Harry Dean Stanton makes a cameo here and has a cheeky nod to his role in the iconic film Alien.
The descriptor of The Avengers makes its way into the movie!
Perfectly hidden behind Tony in this shot as the Battle of New York kicks off is the Shawarma restaurant that the team will eat at in the post-credit scene.
Another Whedon alum appears in the movie with Enver Gjokaj as 'Young Cop.' Gjokaj appeared in Whedon's TV series Dollhouse and would later go on to appear in Marvel's Agent Carter TV series.
'Superheroes...in New York? Gimme a break'
A great reference to the fact that almost all of Marvel's heroes live in the Big Apple.
Our first hint at the coming of Thanos in the mid-credits scene for The Avengers.
The title for the film actually comes from a 2013 comic book event, though the pair share very little in common plot wise beyond the involvement of The Avengers and Ultron.
Thomas Kretschmann appears as Baron Wolfgang von Strucker, an Avengers enemy from the pages of Marvel Comics.
Among the many things hidden in the HYDRA base at the start of the film, the corpse of a Leviathan from the Battle of New York is present.
A parody of the famous "Jesus is my co-pilot" bumper stickers.
In the MCU, Grand Central Terminal has a different statue on top, commemorating the real life heroes from the events of The Avengers.
In reality, the statue is of Hercules, Minerva and Mercury.
Played by Claudia Kim in the film, Dr. Helen Cho is the mother of boy genius Amadeus Cho in the pages of Marvel Comics. Amadeus Cho is among the smartest people in the world in the Marvel Universe and would later go on to become the hero The Totally Awesome Hulk.
As Ultron comes online and begins to scan the internet for information on The Avengers, there are a ton of Easter eggs that flash for just frames on the screen.
Among them are a short recap of the first Iron Man including the famous news paper clipping...
Thor's hammer landing in New Mexico...
Steve's pre-serum form, The Falcon, and SHIELD....
Hawkeye and The Hulk...
and Rhodey as Iron Patriot.
The Falcon even throws in a "cold" nod to their search for The Winter Soldier, aka Bucky Barnes.
Lee appears as a WWII vet who gets drunk from Thor's special alcohol.
As The Avengers attempt to lift Mjolnir, Steve is the only one capable of even budging it which has precedent in Marvel comics. Cap has lifted Mjolnir a few different times in the comics, though some are in alternate timelines/Earths.
Black Widow has also lifted Mjolnir in Marvel Comics though in the alternate reality of What If? Age of Ultron #3.
There are no strings on Ultron or on Disney's Pinocchio.
When Scarlet Witch and Quicksilver confront Ultron he's seen wearing a red shawl, a reference to his alternate identity as The Crimson Cowl.
Though mostly a reference to the events of The Avengers, Ultron's line doubles as a reference to the (retconned) precursor to The Avengers, The Invaders.
The file on Ulysses Klaue features a number of interesting tidbits, but the best is under "Affiliation," noting that he was a former member of The Intelligencia. In the pages of Marvel comics, the group of was a collection of supervillains that also included MODOK, The Leader, and Doctor Doom.
The home of the Black Panther finally gets its first name drop in the MCU.
Continuing the trend of Marvel's Phase Two films that have a character get their arm cut off as a reference to Star Wars: Episode V The Empire Strikes Back.
This also sets up Klau for getting his trademark robotic hand as he has in the comics.
This is a meta-reference to the fact that Jeremy Renner was very publicly not a fan of how his character was mind-controlled for much of the first Avengers movie.
We get a brief glimpse of Black Widows' origin in her Scarlet Witch-induced hallucination, including a cameo by Julie Delpy!
During Steve's portion of the mass hallucination, the band playing at the party are called The Roy Thomas Players. Thomas was a prolific writer for Marvel, penning The Avengers from issue #35 to #104. Some of his creations include Carol Danvers (aka Captain Marvel), Ghost Rider, The Grandmaster, Iron Fist, and Valkyrie.
During Thor's vision of Ragnarok, he sees three figures dressed as a Wolf, a Ram, and a Hart (a deer), which is a reference to the Joss Whedon-created Wolfram & Hart, the inter-dimensional law firm from the Buffy spin-off, Angel.
Also in Thor's dream are the Infintiy Stones assembled together on what looks like the Hand of God.
This is admittedly a little bit mean on Tony's part. The 'Hulkbuster' armor is code-named Veronica with The Hulk's main love interest being named Betty, the pair would form the Archie characters "Betty & Veronica."
This certainly seems like a reference to The Hulk punching Thor out of frame in the first Avengers movie, though with Tony delivering the final blow.
A reference to American playwright and Nobel laureate Eugene O'Neill and his play Long Day's Journey into Night.
Ultron repeats Tony's quip from when he was being created, itself a nod to Neville Chamberlain's speech.
This is a double Easter egg as both Friday and Jacosta are AIs from the pages of Marvel Comics. Friday was created by Tony Stark, while Jocasta was actually made by Ultron himself.
Actor Aaron Himelstein returns as Specialist Cameron Klein, reprising his role from Captain America: The Winter Soldier.
The big takeaway many notice here is that Clint named his newest child after Quicksilver, but his first name, 'Nathaniel,' is a reference to Nathaniel "Natty" Bumppo from James Fenimore Cooper's The Last of the Mohicans. Bumppo was also known as Hawkeye.
Thanos finally puts on his gauntlet and prepares to assemble the Infinity Stones in the final credit scene.
The Children of Thanos are the same characters identified as the Black Order from the 2012 Avengers series. The film includes Ebony Maw, Black Dwarf (renamed Cull Obsidian), Proxima Midnight and Corvus Glaive, played by Tom Vaughan-Lawlor, Terry Notary, Carrie Coon voices and Michael James Shaw.
Thanos is first shown in the film wearing the traditional armor he's worn in the source material and throughout his other appearances in the MCU.
All of this began in 2012's The Avengers as Thanos tried to use Loki and the Chitauri to retrieve The Tesseract, now it all comes full circle in the opening minutes as he finally has it.
The Hulk landing in the Sanctum Santorum comes straight from the Infinity Gauntlet story line, though it was the Silver Surfer that made the landing in the comics....
...and said these words.
Tony makes reference to a dream about having a kid, while the character has a son that operates in the future in the source material.
Thick as thieves in Age of Ultron, this marks the pair's first time on screen since that movie.
Echoing a scene from Guardians of the Galaxy, the origins of the Infinity Stones are recounted and they're all given their proper names.
One of Doctor Strange's arcane items makes its debut.
The events of Civil War are recounted in this one piece of dialogue since The Hulk wasn't present for that encounter.
Tony keeps his cell phone from Steve Rogers from Civil War nearby just in case
Peter's Spider-Sense makes its MCU debut as the hair raises on his arm.
Lee makes his cameo as a bus driver, driving Peter's class to the MOMA for a field trip.
A reference to the character from Spongebob Squarepants.
A version of Peter's classic 'Iron Spider' armor makes its debut in the MCU.
When the Guardians of the Galaxy meet Thor it marks the first time they've interacted with another character from a different series within the MCU.
Since Peter Quill hasn't been on Earth since the 1980s, he has no idea who The Avengers are, plus we get another drop of "Earth's Mightiest Heroes."
A call-back to the first Guardians of the Galaxy movie where Quill uses Kevin Bacon and Footloose as a fable.
A callback to the mining colony seen in the first Guardians of the Galaxy movie.
Though Thor mispronounces it, the actual realm of Nidavellir is the realm of the dwarves from Thor comics and Norse mythology.
The Vision makes his first "human" appearance in the MCU.
The sign seen in this shot, 'We will deep fry your Kebab' was hilarious to the entire country of Scotland who have a love for both kebabs and deep fried food.
Captain America's appearance in Infinity War is reminiscent of the character's time as 'Nomad,' down to the shoulder straps on his outfit.
They may not be sanctioned anymore by the government but the Secret Avengers still use the Quinjet to get around.
The mysterious origins of Gamora are finally revealed in this flashback.
Benicio Del Toro returns as the character, even if it's just an illusion.
David Cross' Tobias Fünke appears in The Collector's collection, a reference to the fact that the Russo brothers previously worked on the hit comedy series.
The things Thanos does to Drax and Mantis with the reality stone are straight out of the Infintiy Gauntlet comic book.
A reference to the McDoanlds character, clearly a staple of Peter Quill's time on Earth.
We return to Avengers headquarters for the first time since Civil War.
Seated next to Secretary Ross is none other than Infinity War co-writer Stephen McFeely!
Though he may not be the Captain anymore, as his suit starts to tear away, the classic "Scales" of the Captain America armor can be seen under his clothes.
Bruce's reunion tour continues as he reunites with Natasha.
T'Challa once again makes reference to Bucky as The White Wolf.
Armless since Civil War, Bucky gets a new arm, and it's seemingly Vibranium to boot!
Game of Thrones star Peter Dinklage appears as Eitri the dwarf, a character from the pages of Marvel comics too.
A call back to Spider-Man's line about 'That really old movie, The Empire Strikes Back' in Captain America: Civil War.
The most famous part of the Iron Spider suit makes their debut as Spider-Man saves Doctor Strange from the suction of space.
Spider-Man finally achieves his goal of becoming an Avenger in the film.
Ever since the first Guardians of the Galaxy, Rocket has had an obsession with removable limbs and body parts, referenced here as he gives Thor a new eye.
Since Thor: Ragnarok established that the Infinity Gauntlet seen in Odin's treasure vault was a fake, Thanos naturally had to forge a new one.
Peter calls back to his Earthly origins.
The name of Thor's new hammer comes from the source material as well as it was the name of fan-favorite Beta Ray Bill's hammer.
The planet with the Soul Stone comes from the pages of Marvel comics.
Thanos' father gets name dropped, Alars. One of Marvel's Eternals, it's possible the character could be referenced in the upcoming movie as well.
If you ever wondered what happened to the Red Skull after he was sucked into space in Captain America: The First Avenger, the character finally makes his return in Infinity War!
A quick reference to the fall out of the Black Panther movie made by Okoye
The Hulkbuster armor returns to the big screen, only this time The Hulk is piloting it.
Once again Footloose and the events of the climax of Guardians of the Galaxy are referenced, only this time Peter Quill bonds with someone who knows exactly what he's talking about.
Like his first hammer, Thor's new one is forged the same way.
Though it may not be Mjölnir, Groot still lifts Stormbreaker in the same way in this iconic shot.
One of Doctor Strange's classic spells from the comics makes its big screen debut as they take on the Mad Titan.
Once again, Rocket really wants an extremity from someone.
Cap and Thor reunite for the first time since Age of Ultron and remark about how they've swapped looks.
A wholesome exchange as Steve doesn't understand Groot just yet.
Doctor Strange uses one of his classic spells, copying himself to confuse Thanos.
Doctor Strange casually namedrops the name of the sequel to Infinity War.
The iconic moment from the Infinity Gauntlet happens in the film.
Seemingly a reference to the world within the Soul Stone itself as the place Thanos finds himself in is orange.
In the comics, the characters that disappear just vanish without a trace, in the film they disintegrate instead.
In the bottom of the screen a scarecrow made of Thanos' armor can be seen in the distance, an image right out of the comics.
After achieving his goal, Thanos retires to a farm, the same thing he did in the comics.
The pair of SHIELD agents return for the post-credit scene and are quickly snapped away.
Fury manages to hit a button on a pager before disappearing, which sends a signal to none other than Brie Larson's Captain Marvel....wherever she is!
A reference to how the other Marvel movies end with a coda that they will return, but now with the big bad.