With production finished on Avengers: Infinity War and Avengers 4, Marvel is moving on to more of 2019's movies. Filming has kicked off on Captain Marvel, with Brie Larson heading to California to film her first scenes in costume. Naturally, set photos quickly hit the Internet - and took fans by surprise. Concept art had led fans to expect a version of Captain Marvel's iconic red-and-black costume. Instead, the photos showed Larson wearing an outfit that was green and gray.What's going on? And what does this costume actually mean?

Carol Danvers is Working with the Kree

In the comics, Carol Danvers was an agent in the US Air Force who wound up working alongside an alien race known as the Kree. Specifically, she became an ally of the Kree warrior Captain Mar-vell. That led to her body being irradiated with alien energy, imbuing Carol with Kree powers. She initially took up the superhero identity of Ms. Marvel, but ultimately claimed the identity of Captain Marvel in honor of the fallen Kree hero.

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It looks as though Captain Marvel will follow a similar structure. Larson has been visiting USAF bases to get a sense of how the Air Force operates, and has even taken flight training. It's safe to say Carol's USAF background will be retained for the film, and the fact Larson actually went through training is exciting. Meanwhile, Jude Law has been cast as Mar-Vell, so Carol's friend and ally will appear in the film as well. This time around, though, Carol Danvers's costume suggests an ever closer link. Somehow, Carol will wind up wearing the distinctive uniform of a Kree Captain.

One of the set photos shows Carol gripping a man's arm, pushing him to the ground. It seems clear she already has super-strength, so these scenes take place after she has already been given her the Captain Marvel powers.

The Comic Book Inspiration for Captain Marvel

Marvel visionary Kevin Feige has already confirmed that Captain Marvel will be partly inspired by a classic arc known as the Kree-Skrull War. Avengers writer Roy Thomas drew inspiration from Raymond F. Jones's This Island Earth. He imagined a story in which the planet Earth became caught in the conflict between two vast, powerful alien races - neither of whom cared whether or not Earth survived. The planet became the cosmic equivalent of a Pacific island in World War II, with native islanders horrified as the Americans and the Japanese waged war on their shores.

In the early 2000s, Marvel launched the so-called "Ultimate Universe" - a modernized relaunch of their key series. Although this was initially much more grounded, as time passed Marvel continued to embrace the cosmic aspects of their franchises. In 2005, the Ultimate Secret miniseries introduced a reimagined version of the Kree race, along with Mar-Vell himself. In the Ultimate Universe, the Kree were aware of a world-ending threat that was headed straight for Earth. They intended to sabotage humanity's attempts at space exploration, and so ensure our race was rendered extinct. Mar-Vell rebelled against this, and chose to help humanity survive the threat of Gah Lak Tus.

The Marvel movies have always tended to draw inspiration from the Ultimate Universe. Significantly, Brie Larson's costume is actually a blend of the tradition Mar-Vell outfit and the one he wore in Ultimate Secret. These first set photos definitely tease that the Ultimate Universe is continuing to influence the MCU - and will perhaps inform the plot, as well.

The '90s and the Space Age

This may offer a subtle clue as to why Captain Marvel is set in the '90s. Until the '90s, space exploration was essentially caught up in the Space Race - a period of intense rivalry between the United States and the U.S.S.R.. The fall of the Berlin Wall changed everything, though, and humanity began to focus on space exploration as an end in itself. The Hubble Space Telescope was launched; construction began on the International Space Station; and NASA landed the Pathfinder on Mars. Before the '90s, space exploration had been a matter of intense rivalry. Now, humanity was looking outwards. Significantly, the USAF maintained a strong connection tie to the American space program.

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In the context of the MCU, in the '90s humanity was taking its first faltering steps into space. And it looks as though that drew attention - from both the Skrulls and the Kree. Neither race will be on Earth with humanity's best interests at heart. Both are really focused on defeating the other in battle. It's possible that, in a plot thread lifted from Ultimate Secret, one or both races may intend to prevent humanity reaching the stars.

How Captain Marvel Connects to the Rest of the MCU

But how does Captain Marvel fit into the broader MCU? So far, there seem to be three ways.

The first, of course, is that the film will feature Samuel Jackson's Nick Fury. It seems likely this will be S.H.I.E.L.D.'s first contact with aliens, and they will swiftly learn that humanity is very vulnerable indeed. Curiously, though, Fury would be unable to get funding for aggressive defense projects until over a decade later - when Thor battled the Destroyer. It seems likely the events of Captain Marvel will be hushed up, and possibly all evidence of alien involvement destroyed. Although Fury is left watchful, confident that aliens will return, he's not able to actually prepare for them.

The second is the Quantum Realm. Introduced in Ant-Man, the Quantum Realm is another plane of reality, an alternate dimension reached by Scott Lang. Quantum physicist Dr. Spiros Michalaki, one of Marvel's consultants, has already confirmed that the Quantum Realm will appear in Captain Marvel. Significantly, in the comics Kree warriors typically wear "Nega-Bands" - wrist bands devices that grant their wearers tremendous power. These Nega-Bands were based on Quasar's "Quantum Bands," and draw their power from a realm of potential energy known as the Quantum Zone. It seems likely that a version of the Nega-Bands will appear in the film, although it's worth noting that Larson's gauntlets don't seem to be prominent enough to be Nega-Bands themselves.

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The final link is a simple thematic one. Although Captain Marvel is set in the '90s, the film is releasing between Avengers: Infinity War and the as-yet-untitled Avengers 4. Given that's the case, it's surely no coincidence that Captain Marvel will tell the tale of Earth's first contact with aliens - while both Infinity War and Avengers 4 will see the Earth battle to survive the threat of Thanos. In both cases, humanity has drawn attention to itself, and will likely regret that fact.

The Red-And-Black Costume will Appear

It's worth stressing one final detail. Brie Larson may be wearing gray-and-green in these set photos, but she'll inevitably move to the classic color scheme by the end of the film. Concept art released at last year's San Diego Comic-Con showed Carol Danvers in her traditional red-and-black. There's no way Marvel would officially release concept art that was so different to the finished product.

That fact subtly reshaped our understanding of the scene. Carol has allied with the Kree, and claimed the uniform of a Kree Captain. That doesn't mean she'll work as their ally throughout the film, nor does it mean that the Kree - as a race - are the "good guys." It simply means that, in this scene, Larson will have formed some sort of alliance with the Kree, or perhaps will have returned to Earth after having infiltrated the alien race. By the end of the movie, fans should expect Captain Marvel to don a more traditional costume, and it's likely set photos will show that outfit when filming resumes in March.

Captain Marvel remains a subject of mystery. Why is the film set in the '90s? How will Mar-Vell be portrayed, and will Carol Danvers wind up allying with the Kree? These first set photos have offered some intriguing hints, and fans are sure to examine every future photo in search of more clues.

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