Both Marvel Studios and DC have made a big effort to fit hidden secrets in their cinematic universes, whether they be references to the comic book source material from which these movies originate, subtle foreshadowing to the future of these cinematic universes, references to obscure comic book characters, or even just references to other popular franchises that the filmmakers happen to be fans of. It adds an extra layer of fun for fans of these movies to obsessively comb through every frame to find these little secrets, and some of them are so well hidden that they still have yet to be found.

RELATED: 15 Disney Easter Eggs And Hidden References In The MCU

Even in films that are almost 10 years old, we're still finding new and interesting hidden Easter Eggs that just make us want to go through every movie again to see what we missed! Even if you think you've seen all there is to see and you know every Easter Egg that Marvel and DC have ever put into their films, we're pretty positive that there are a few that you missed. You've combed through the easily-found Easter Eggs that people noticed on their first viewing, but we found 10 Easter Eggs from the MCU and 10 from the DCEU that there's no way you caught your first time!

20 THE EMPIRE STRIKES BACK... AGAIN (MARVEL PHASE 2)

After Disney's acquisition of Lucasfilm, fans started to notice Star Wars references popping up a lot more frequently, but one of the best and most subtle is a recurring theme of characters losing their right hands throughout every single project of Phase 2 as a reference to Luke losing his hand at the end of Empire Strikes Back.

Killian in Iron Man 3, Loki while disguised as Thor at the end of Thor: The Dark World, Bucky Barnes in Captain America: The Winter Soldier, Nebula (and Groot) in Guardians of the Galaxy, Dr. Ulysses Klaue in Avengers: Age of Ultron, Yellowjacket's right arm is the first thing to disappear in the finale of Ant-Man, and even Phil Coulson loses his hand in the finale of Agents of S.H.I.E.L.D. season 2!

19 I CAN DO THIS ALL DAY (CIVIL WAR)

In the finale of Captain America: Civil War, when Captain America and Iron Man are fighting, both of them have been beaten pretty badly and Cap wipes blood from his lip and says, "I can do this all day." If you haven't been constantly marathoning the Marvel Cinematic Universe on a loop, you might have missed that this was a callback to a line Steve said in his very first fight of the MCU when he was still just a scrawny kid getting beaten up by bullies in Captain America: The First Avenger.

Before Bucky comes to his rescue, Steve holds up a trash can lid like a shield and says, "I can do this all day." It indicates that things have come full circle for Steve, and he leaves the shield behind indicating that everything that comes after will be part of a new beginning.

18 THE LEADER (THE INCREDIBLE HULK)

The Incredible Hulk is undoubtedly the strangest entry in the entire Marvel Cinematic Universe. It's not a particularly bad movie, but it's pretty forgettable; so much so that Marvel Studios has barely made any reference to it since, despite the fact that it was clear it was being set up for future sequels at the time.

The clearest instance of this is toward the end of the movie when Dr. Samuel Sterns starts to mutate before the camera cuts away, foreshadowing his transformation into the Leader, one of Hulk's greatest villains from the comics. It's possible Marvel could revisit this someday, but since Hulk is unlikely to get another standalone movie again thanks to some rights issues with Universal Studios, it's probably become nothing more than a subtle nod to the comics now.

17 S.H.I.E.L.D. HERO CATALOGUE (IRON MAN 2)

Iron Man 2 was the point where the cinematic universe really started to take shape. Nick Fury was talking about The Avengers and we got to see Captain America's shield and Thor's hammer. So it's pretty clear that this was around the time when the real planning for the future started to take place.

Eagle-eyed fans may have seen the first indications of just how big things were going to get in the scene when Tony is talking to Nick Fury toward the end of Iron Man 2, where you can see a map in the background with big orange circles indicating the locations of potential superheroes, including one in New Mexico where Thor's Hammer would be found, one in Africa that can only be Black Panther, and one in the middle of the Atlantic Ocean, presumably indicating Namor.

16 RHODEY'S RINGTONE (IRON MAN)

One of the coolest scenes in the first Iron Man movie is just after Tony takes the Iron Man suit into combat for the first time. On his way back to the United States, he's intercepted by two fighter jets. When Tony calls Rhodey during the dogfight to convince him to call off the jets, Rhodey pulls out his phone and the ringtone is a midi version of the theme music from the 1966 Iron Man Cartoon played at a slightly higher tempo.

It probably wouldn't have been an easy reference to spot for the modern younger fans, but for older people in the audience with a keen ear, it was a nice little callback to what could have been their first exposure to the character of Iron Man.

15 THE TEN RINGS (ANT-MAN)

The first glimpse we got of the Ten Rings was in the first few minutes of the first Iron Man. The terrorists who kidnap Tony make a ransom video and behind him is a banner with the Ten Rings logo. They come up again in Iron Man 3 with the Mandarin and are seemingly dismantled, but we get another glimpse of them in Ant-Man.

When Cross meets with his investors about the Ant-Man technology, one of the men has a Ten Rings tattoo on his neck. It's partially obscured by his suit, but a clear callback to the same symbol that appeared behind Tony Stark in the first Iron Man, which means that they're still out there, working in the shadows, and almost sure to show up again in the future.

14 THE DUALITY OF SPIDER-MAN (SPIDER-MAN: HOMECOMING)

The Marvel Cinematic Universe has done a great job so far of mimicking iconic comic book art from the source material as a nod for long-time readers, and with the release of Spider-Man: Homecoming, the studio got a chance to recreate one of the most recognizable images from Spider-Man comics ever.

When Peter is trapped after a confrontation with the Vulture resulting in the collapse of a warehouse on top of him, he looks into the puddle below him and sees his face half-reflected next to his mask. This is a common image throughout the history of Spider-Man comics, typically appearing when Peter's Spider-sense goes off or to symbolize a moment when he has to reconcile the responsibilities of his normal life with the responsibilities of being a superhero.

13 COSMO: THE TALKING RUSSIAN DOG (GUARDIANS OF THE GALAXY)

It's safe to say that the Guardians of the Galaxy were Marvel's least well-known property by general audiences before the first film came out, and that film didn't start things off with the original Guardians crew, so a lot of the references were bound to go over people's heads. A lot of those references appear in one specific scene of the movie.

When the Guardians go to visit the Collector, one of the items in his collection is a dog dressed in a Soviet astronaut suit. This is a callback to the original Guardians of the Galaxy where Cosmo, the talking Russian dog, was a part-time member of the Guardians team. Also in his collection were one of the space slugs from James Gunn's Slither and of course, Howard the Duck.

12 PUNCHING A NAZI (CAPTAIN AMERICA: THE FIRST AVENGER)

Captain America: The First Avenger is full of references to the early days of Captain America comic books, from his original shield to early costume designs and classic characters, but you can't call back to anything earlier than the cover art of the very first Captain America comic ever published, which is exactly what they did.

During one of the USO shows, Cap participates in a little sketch where an actor portraying Hitler sneaks up on him before Steve turns around and punches him in the face. This is a direct recreation of the cover of the very first Captain America comic book cover in 1941 where he punches out the real Hitler. Steve doesn't meet the real Hitler in the movie, but presumably still brings down the Nazi regime by taking out the Red Skull.

11 ANT-MAN ARROW (CAPTAIN AMERICA: CIVIL WAR)

Captain America: Civil War was the biggest gathering of Marvel superheroes on-screen to date, allowing Marvel the unique chance to recreate some of the most iconic moments of old Avengers comics, and thankfully screenwriters Christopher Markus and Stephen McFeely fulfilled a major fan request by recreating one in particular.

The shot of Ant-Man riding Hawkeye's arrow was pretty iconic before it appeared in the movie. It was featured on the cover of 1963's The Avengers Vol 1 #223 by writer David Michelinie and artist Greg LaRocque. More modern audiences might know it better from the animated series Avengers: Earth's Mightiest Heroes. Several other incarnations of the Avengers have also used the move throughout the years, so long-time comic readers and new fans alike got a nice recreation of the iconic Avengers cover.

10 HARLEY HELPED KILL ROBIN (SUICIDE SQUAD)

One of the biggest mysteries of the DCEU currently surrounds the death of Batman's sidekick, Robin. We know that he was murdered, presumably by the Joker, thanks to a shot in Batman v. Superman: Dawn of Justice, which shows Robin's bullet hole-riddled suit with a message from the Joker reading, "Hahaha, Joke's on you, Batman."

When Waller introduces Harley Quinn at the beginning of Suicide Squad, her title card features a long dossier on her criminal career, one item of which rolls by quickly enough that you might miss it on your first viewing, but it points to Harley Quinn's involvement in Robin's death reading: "An Accomplice to the murder of Robin." We don't know how involved she was, but presumably, we'll learn more if and when The Batman comes out to fill in that particular backstory.

9 SHAZAM! (BATMAN V SUPERMAN)

The DCEU is kind of trying to play catch-up with Marvel to build its cinematic universe. Batman v. Superman: Dawn of Justice was only the second movie in that universe, but they used it to tease every upcoming hero for the next several years. We met Wonder Woman and Batman, and saw short clips of Cyborg, Aquaman and The Flash, but that may not have been the only teaser we got.

When Alfred is trying to teach Bruce Wayne about morality and corruption, he hints at Shazam's possible introduction to the DCEU saying, "Everything's changed. Men fall from the sky, the gods hurl thunderbolts, innocents die." The first and last line could be in reference to Superman, but gods hurling thunderbolts won't happen on-screen until another movie on the DCEU's production slate: Shazam. Does he already exist in this universe? This could just be us projecting. But it could also not be.

8 PARADISE ISLAND (WONDER WOMAN)

The DC Comics universe has been pretty static over the years, with origin stories and histories frequently going through alterations big and small. Wonder Woman managed to pay respects to the complete history of the character in many ways that the rest of the films in the DCEU haven't quite accomplished yet

One clear example of this is at one point early on in the film when Steve Trevor refers to Diana's homeland, Themyscira, as "Paradise Island," which is a callback to the original name of Wonder Woman's home in the comics. The name "Themyscira" wasn't introduced until 1987 after the legendary Crisis on Infinite Earths storyline and the relaunch of the Wonder Woman series with Wonder Woman Vol. 2 #1 by writer Greg Potter and artist George Perez.

7 THE ALEX ROSS COVER (SUICIDE SQUAD)

Marvel isn't the only studio to recreate legendary comic book art in its films. Batman v Superman: Dawn of Justice takes a few shots directly from Frank Miller's The Dark Knight Returns, and Suicide Squad recreates an iconic Alex Ross variant cover from a one-shot comic titled Batman: Harley Quinn.

When Amanda Waller is describing Joker and Harley as "King and Queen of Gotham" at the beginning of the movie, it cuts to a shot of the two dancing in an exact recreation of Alex Ross's iconic cover with Margot Robbie in Harley Quinn's classic jester outfit and the Joker in a tuxedo. It even goes so far as to mimic the dark lighting scheme from the original painting. There was a lot of criticism for Harley Quinn's outfit in Suicide Squad, but we can at least be thankful she didn't wear that the whole time.

6 WEISINGER PRIMARY SCHOOL (MAN OF STEEL)

Man of Steel was the first entry into the DC Extended Universe, and while it's far from a perfect Superman film, Zack Snyder made sure to acknowledge and pay respects to the character's roots. One particular moment passes by pretty quickly and could have been easily missed by anyone without an extensive knowledge of Superman comic book history and a keen eye.

Towards the end of the movie, Martha Kent is looking through her destroyed house and finds a photo album, where there's a shot of young Clark Kent winning a science fair medal in front of a blurry sign for Weisinger Primary School named in dedication to legendary Superman editor Mort Weisinger who oversaw the Silver Age of Superman comics in the '50s and '60s.

5 RICHARD DONNER'S SUPERMAN IS CANON (BATMAN V SUPERMAN)

In Batman v. Superman: Dawn of Justice, we meet accidental terrorist Walter Keefe, who blames Superman for his paralysis thanks to the battle with the Kryptonians at the end of Man of Steel which destroyed Metropolis. At one point, we see the inside of Keefe's apartment and a shrine wall that he's built to Superman containing newspaper clippings of Superman's various exploits.

One of these newspaper headlines reads "Superman Shifts Tectonic Plate; Prevents Devastating Earthquake," which is a callback to the earthquake that killed Lois Lane in the first Superman movie until he reversed the turn of the Earth and went back in time to fix it. This could easily be an indicator to the audience that the events of Richard Donner's Superman are canon with this universe, but if not, it's still a nice callback to the movie that brought Superman to the mainstream.

4 CATCHING THE BULLET (WONDER WOMAN)

It doesn't necessarily have to be a Superman movie to make a reference to the classic Superman films. They're a big part of DC cinematic history and they helped to pioneer the modern superhero film genre. In another nod to Richard Donner's Superman, in the scene where Steve and Diana are confronted in an alleyway by one of Ludendorff's spies, Steve is in the path of a bullet before Diana reaches out and stops it with her bracer.

Director Patty Jenkins confirmed this was a nod to the scene in the original Superman film when Clark Kent catches a bullet aimed at Lois Lane. Diana and Clark are even wearing practically the same outfit in a long gray overcoat with a wide-brimmed fedora and black glasses.

3 HARLEY'S BAT (SUICIDE SQUAD)

For all its flaws, Suicide Squad did a lot to make subtle callbacks to the members' histories. Some of them aren't even noticeable unless you freeze-frame the movie or look at behind-the-scenes photos, like the text that wraps around Harley's bat, which is a word-for-word recreation of a lullaby she sings over the end credits of Batman: Arkham City

It contains too much rough language and violent imagery to print here, but to summarize, it takes the lyrics of "Hush little baby," and alters it to talk about violently murdering people, painting the streets with blood, and building a legacy of crime. It ends with the line, "And if you grow up with his smile, momma's gonna be so proud of you," leading us to ask, is there a baby Joker out there somewhere in the DCEU?

2 KEEP CALM AND CALL BATMAN (MAN OF STEEL)

The DCEU has gotten a lot of criticism since Batman v. Superman: Dawn of Justice for trying to cram in too much early on and build their cinematic universe prematurely. It can be especially jarring at times since Man of Steel seemed content with allowing Superman some breathing room to build the universe one character at a time.

However, if you look closely, the hints at other superheroes already existing in this universe are still there in Man of Steel. The Wayne Industries logo can be seen on a satellite at one point in the film, but even more overt is in the background of one scene when the city is being destroyed by Zod, a poster that reads "Keep Calm and Call Batman" can be spotted on the wall.

1 WHO WATCHES THE WATCHMEN? (BATMAN V SUPERMAN)

We may never get to see the characters from Watchmen in the DCEU in all their glory, but that doesn't mean that they don't exist in the universe to some extent. After all, Zack Snyder directed Watchmen four years before Man of Steel, and in the comics, after DC's Rebirth event, the Watchmen joined DC's main continuity, so however unlikely, it's not impossible.

Perhaps the most intriguing thing about this possibility though is that we've already gotten a little hint that they exist in some form whether as fictional characters or real heroes who were active in the '80s. During the fight between Batman and Superman, a graffiti tag on the wall reads, "Quis Custodiet Ipsos Custodes?" which translates from Latin to "Who watches the Watchmen?"

Have you caught any other Easter Eggs in the DCEU or MCU that most folks don't know? Enlighten us in the comments!