Look, it’s no secret that the Marvel Cinematic Universe is jam packed with characters. There are so many, in fact, that half the cast of the upcoming Avengers: Infinity War can’t fit all of them on its poster (or the actors’ names for that matter). This sort of over-stuffed existence it to be expected over the course of a decade filled with 18 films, over a dozen seasons of television, and several short films. New fans who are unfamiliar with the source material have gotten to know characters that have been around for decades, but have never graced the screens of televisions or theaters. And old fans have gotten to see the adventures of superheroes and their battles with villains come to life (it truly is an amazing time to be geek).

But among all the well-known and over-exposed characters of the MCU, there are lesser seen heroes and villains hiding in their ranks. Characters who may not fully represent their comic book counterparts are wedged in the nooks and crannies everywhere. From in name only adaptations to wildly different backgrounds, there are Marvel characters that even the most ardent comic fans may have easily let slip by their geek radar.

15 RED HULK

General Thaddeus E. "Thunderbolt" Ross is one of The Incredible Hulk’s primary villains in comic books. He’s a brilliant military tactician and all around tough guy (not to mention the father of Bruce Banner’s love interest, Betty Ross). Thunderbolt was eventually reintroduced to the Marvel Universe as Red Hulk in Hulk Vol. 2 #1. And just as his moniker would imply, he’s even angrier than the big, green guy we all know and love.

Thunderbolt is no stranger to the Marvel Cinematic Universe, but he is often over looked despite being portrayed by the brilliant actor, William Hurt in The Incredible Hulk and Captain America: Civil War. The fact that Hurt’s Thunderbolt has the longest absence of any MCU character between films (he was missing in action from the franchise for eight years) doesn’t exactly make him a constant presence, so it’s easy to forget he’s a key player.

14 THE SCORPION

Actor Michael Mando appears in the film Spider-Man: Homecoming as a criminal looking to purchase weapons from the Vulture during the epic Staten Island Ferry scene. While his inclusion may seem completely happenstance to lead to the inevitable bifurcation of the boat, it turns out Mando was actually playing the character of Mac Gargan, which is the alter ego of the Scorpion.

The filmmakers were a little less than subtle with regards to Gargan’s inclusion, especially in the mid-credits scene during which he approaches Toomes about Spider-Man and a scorpion tattoo is clearly visible on his neck. The little exchange these two characters had also led audiences to believe that a potential Sinister Six scenario could be on the horizon. Thankfully it was handled with a bit more grace than it was in previous Spidey films.

13 ADAM WARLOCK

The fact that Adam Warlock has yet to make his big screen appearance properly (especially with the inclusion of the Infinity Gauntlet) makes his bizarre cameos in the MCU thus far even stranger. Adam Warlock is a heavy hitter in the galactic side of the Marvel Universe. He as a key player in the comic mini-series Infinity Gauntlet and its sequels. Which is why is seems a bit odd that the films have only shown him as a cocoon. Let us explain:

In the first Guardians film, we see a bulbous sack in one of The Collector’s display boxes. It’s easy to miss, but like everything in those boxes, it hold some massive significance. This weird sack holds Adam Warlock. In fact, it actually births him. The cocoon is seen again (this time less gross) in the second Guardians film and is even called “Adam” by Ayesha.

12 AMADEUS CHO

It ain’t easy being green. But sometimes it is totally awesome. At least it is if you Amadeus Cho, a young, brilliant scientist who takes on the mantel of Hulk. Amadeus is a fan-favorite among comic readers and gave us a fresh take on a superhero we thought we knew inside and out. But before he became Hulk in the comics, Amadeus made a cameo appearance in one of the earliest installments of the MCU film series.

In The Incredible Hulk, Martin Starr (Silicon Valley) plays a lab technician who is bribed with pizza by Bruce Banner in order to gain access to a lab. In the film, Starr is uncredited and unnamed, but in the film’s novelization is his referred to as Amadeus Cho. Now Starr bares little resemblance to the character in the comic books, but this easter egg is a fun nod to the character.

11 MADAME MASQUE

Supervillain Madame Masque has been a scourge in Marvel Comics since the late ‘60s. She’s been an enemy of several Avengers, including Iron Man, Doctor Strange, and Hawkeye over the years, and has made some massive power moves in the Marvel Universe. Based on her track record, it would make sense that she would be included in the MCU in some fashion, which she was in the television series Agent Carter.

Her alter ego, Whitney Frost makes an appearance in the show as a '40s wartime inventor, portrayed by actress Wynn Everett. While this version of Frost never dons her gold visage from the comic books, she is a formidable villain who is sadly defeated in the season two finale of the show, which happens to be the final episode before the show’s cancellation.

10 NUKE

Nuke was a disturbed Vietnam War veteran who first appeared during Frank Miller and David Mazzucchelli’s legendary run on Daredevil. With modern day understanding of PTSD among veterans and the real world consequences of its effect, the original incarnation of the character hasn’t exactly aged well. However, a version of Nuke has popped up in the MCU.

In the Netflix series, Jessica Jones, a character by the name of Will Simpson (a nod to Nuke’s real name Frank Simpson) is one of the show’s reoccurring antagonists. This version of Nuke is a police sergeant who at first looks to help our heroes until he falls under the influence of Kilgrave. And just like his comic book counterpart, Simpson is a former special ops soldier and undergoes pharmaceutical experimentations that turn him into a stark raving lunatic.

9 THE TINKERER

Spider-Man’s roster of D-list villains is as expansive as it is ridiculous. From old men with wings to multiple people who wield the power of electricity, old web head has his hands full with a plethora of baddies. But one villain who connects several members of Spidey’s rogue’s gallery. Phineas Mason (aka The Tinkerer) is a brilliant inventor who designs weapons and armor for some Spider-Man’s most notorious rivals.

One could be forgiven for having missed Mason’s appearance in the MCU. In the comics, he’s portrayed as a balding, elderly man with thick glasses and a hooked nose. However, in Spider-Man: Homecoming, Mason is played by Michael Cernus (Orange Is the New Black) who bears little resemblance to his character’s comic book counterpart. To casual viewers, he was just another guy on the Vulture’s crew.

8 CHARLIE-27

Huge chunks of the Guardians of the Galaxy films are filled with callbacks, references, and character cameos from the comics. Sometimes it’s a bit on the nose like the fun stinger featuring Howard the Duck or it’s a quick shot of a Dark Elf locked up in The Collector’s…um, collection. But there are some easter eggs that are somewhere in between that are often overlooked, ignored, or completely forgotten.

One such character appearance was by an original Guardian. Charlie-27 was one of the Guardians of the Galaxy from the 31st Century and has been appearing in comics since 1969. In the film Guardians of the Galaxy Vol. 2, Charlie-27 is portrayed by Ving Rhames (Pulp Fiction) as a Ravager Faction Leader, which is a departure from the iteration of the character in the comics, but works well in the context of the film.

7 HELLCAT

Patricia “Patsy” Walker has a strange history in comic books. She was originally the star of teen romantic comedy comic books from the '40s to the late ‘60s. She later appeared a few years later as the crime-fighting Hellcat and eventually joined The Defenders. This might be one of the starkest character changes in Marvel history. Hellcat would continue to charm readers for decades and even play supporting roles in several of the more recent Marvel Comics relaunches.

But Patricia Walker is no stranger to live action adaption. She is the best friend to hard-drinking, private detective Jessica Jones in her Netflix series. While Trish never dons the moniker of Hellcat in the show, she does display some fighting and acrobatic prowess. She’s a pair of yellow tights away from giving comic fans the Hellcat they’re familiar with.

6 COLDBLOOD

Eric Savin (better known as Coldblood) first popped up in Marvel Comics Presents #26 back in 1989. Savin’s story is pretty tragic. He was a United States Army colonel who is blown to bits by a land mine, only to be put back together using cybernetic implants through the secret government experimental wing known as Project: Ultra-Tech. Savin would on to grapple with the existential horror his new implants (you know, that old chestnut) while pursuing a career as a mercenary.

The version of the character that showed up in Iron Man 3 (played by actor James Badge Dale) did in fact undergo experimentation, but it was to boost his combat abilities through the Extremis treatment. Aside from never being regarded as Coldblood, the absence of any morality from Savin in the film is the biggest departure from the character’s comic version, which makes the connection pretty thin.

5 THE OWL

Leland “The Owl” Owlsley has been a foil to Daredevil since the beginning of the Man without Fear’s crime-fighting career. While his appearances in the comics have diminished over the years (there’s only so much mileage you can get out some avian-based villains), he has not been completely forgotten.

Owlsley, portrayed by the amazingly talented character actor, Bob Gunton (The Shawshank Redemption) was one of the minor villains in the first season of the Netflix series Daredevil. Some fans may not have picked up that this character was in fact The Owl. The on-screen version did not process any of the avian qualities The Owl is known for from the comics. And unfortunately, there won’t be any further development of the character since Wilson Fisk tossed him down an elevator shaft (bet he wished he had those avian qualities).

4 STARHAWK

The final moments of Guardians of the Galaxy Vol. 2 are filled with myriad cameos by characters from Marvel Comics, some them never being mentioned by name. During the funeral for Yondu Udonta, several Ravager factions attend to honor their fallen brethren who was now redeemed in their eyes after years of exile. It’s a wonderfully touching farewell moment and it hold even more weight when you consider who some of those attendees were.

The most prominently featured in the film was Sylvester Stallone’s character Stakar, who in the comics was Starhawk, one of the original Guardians of the Galaxy from the 31st Century along with Yondu. Yet another attendee at Yondu’s funeral also donned the moniker of Starhawk: Aleta Ogord, who is played by Michelle Yeoh in the film. So that’s two Starhawks most viewers didn’t even know they had.

3 BARON ZEMO

Captain America: Civil War leads to a massive battle between Avengers and a very personal standoff between two men who have the same goal in mind but either with their own divisive methods to make that goal come to fruition. The film is stuffed with so much dramatic subterfuge, emotional rollercoaster, and eye-popping action that it’s easy to forget how the chain of events that led to these monumental moments were ever set in motion in the first place. The catalyst, the agent of chaos who lights the spark is Helmut Zemo.

It’s surprisingly easy to forget Zemo is the real villain of film despite Daniel Brühl’s amazing performance (what with everything else happening). It’s not to say audiences don’t recall that there was a saboteur behind everything, but without his purple hood and military outfit, it can be difficult to identify him as Baron Zemo.

2 RAZA LONGKNIFE

In the inaugural film of the MCU, Iron Man, a terrorist group known as The Ten Rings (a nod to the Mandarin’s source of power in the comics) kidnap Tony Stark and hold him hostage. The leader of the sect imprisoning Stark goes by the name Raza (played by Faran Tahir) and winds up getting sever facial burns during the film’s titular superhero make a break for it. A viewer with a keen eye (and an open mind) can see that this in none other than the Marvel Comics character, Raza Longknife.

Raza in the comics has a wildly different background. The character was the sole survivor of an alien race and member of the space pirates team, Starjammers. But with the MCU taking huge liberties with characters and their origins, we appreciate any incorporation of strange heroes we can get, even if they are portrayed as villains.

1 UNION JACK

James Montgomery Falsworth was a British adventurer and government operative who took up the mantle of Union Jack during World War I and World War II, fighting against the German armies and their vampire supervillain, Baron Blood. Falsworth’s early battles were pulpy and patriotic in the same vein as similar exploits of Captain America. In the current Marvel Comics landscape, Falsworth is little more than a distant memory since the character peacefully passed away. But the mantle of Union Jack lives on, being passed on to new heroes.

Falsworth, however, has existed outside the comics, and made a cameo appearance in Captain America: The First Avenger as a British P.O.W. held captive by HYDRA. The original Union Jack never dons his superhero moniker or costume in the film, but actor JJ Field’s cameo is a wonderful nod that many fans missed.