Mild spoilers for Agents of S.H.I.E.L.D.'s season 5 premiere
While Agents of S.H.I.E.L.D. began as a show reacting to the larger events of the MCU, it's grown into a series entrusted with some core characters and storylines from Marvel Comics. Ghost Rider, Inhumans, and LMDs all debuted on the show, and recent comic arcs like Inhumanity have more or less played out on the series. With the arrival of season 5, the agents have made the jump to space and once again come face to face with the Kree.
Before the intergalactic race appeared in Guardians of the Galaxy, the Kree first appeared on Agents of S.H.I.E.L.D. Moreover, they have a far larger impact on the television side of the MCU than the films so far. That will all change when Captain Marvel makes them integral to its plot by adapting the Kree-Skrull War, but given how essential Agents of S.H.I.E.L.D. has been to laying groundwork in the MCU, could the Skrulls make their debut on the series first to kick off Secret Invasion?
What Is Secret Invasion?
Created, like much of the Marvel Universe, by Stan Lee and Jack Kirby, the Skrulls debuted back in 1962's Fantastic Four #2. Over the decades, their history has been fleshed out and their animosity towards the Kree has been a key part of their story. Crafted by the Celestials from a primitive race, the Skrulls evolved into three different species that constantly warred. Eventually, the branch that possessed shape-shifting abilities won out, and went out into the cosmos to impose their will on other civilizations.
When the Skrulls arrived on Hala, they pit the planet's two races—the war-like Kree and the peaceful Cotati—against one another in a contest of technology. Before the winner had been decreed, the Kree slaughtered the Cotati and attempted to claim victory. The Skrulls were not pleased, leading to the Kree killing them as well and using their confiscated technology to jumpstart their empire. By the time word of this reached the Skrull homeworld, the seeds of the Kree-Skrull War had been planted.
The conflict itself raged for thousands of years, but the Kree-Skrull War that most comic fans refer to is the event that played out in Avengers #89–97 in 1971 and '72. It's that conflict that Mar-Vell and Carol Danvers played a role in, and its sequel in the early '90s will also likely inform Captain Marvel. When it comes to the Skrulls, however, the arc is second only to Secret Invasion.
After the cosmic Annihilation story left the Skrull Empire in ruins, the race began their revenge: a massive, covert invasion of Earth using shape-shifted Skrulls as sleeper agents. Written by Brian Michael Bendis, the event stretched across 2008 and '09 in an 8-issue comic and a variety of crossovers and spinoffs. Dozens of prominent heroes and villains were revealed to be Skrulls in disguise, a storyline that led to paranoia, shattered alliances, and the opportunity to retcon a number of backstories. The fallout of the event created new stories of its own and the fear the Skrulls sewed is still present in the modern Marvel Comics universe.
With Phase 4 set to tell a brand-new story in the MCU off the back of a cosmic clash, the news that Captain Marvel would introduce the Skrulls solidified years of fan theories that Secret Invasion is coming to the big screen. But given the complex nature of the story and the seeding required to set it up, could the now-intergalactic Agents of S.H.I.E.L.D. tackle the event instead?