Captain Marvel hit theaters in March 2019 and quickly became one of Marvel’s highest-grossing films. It's also at the center of online speculation heading into Avengers: Endgame. While the cinematic debut of Carol Danvers does lead directly into the fourth installment of the Avengers franchise, it could also serve as a springboard for the future of the Marvel Cinematic Universe (MCU) beyond Endgame.
For years, fans have guessed that the MCU will adapt Brian Michael Bendis and Leinil Francis Yu's 2008 crossover event, Secret Invasion, in which the Skrull Empire attempts to conquer Earth and make it their new homeworld. This decades-long mission ultimately results in several heroes and villains secretly being replaced by Skrulls. Following Captain Marvel's big twist - in which the Skrulls are revealed to be benevolent, and the Kree turn out to be the real villains - most theorists have concluded that Secret Invasion isn't coming to the big screen. A closer look at the events and characters of Captain Marvel reveal, however, that the film left the door wide open for a Skrull takeover of the MCU.
The fabric of the Marvel Cinematic Universe is so tightly woven that “plot holes” often turn out to be intentional loose ends. One such example in Captain Marvel involves a Skrull who is missing on Earth. Talos arrives on Earth with three other Skrulls; however, by the film’s conclusion, two of them have been taken out and one is mysteriously absent. This missing Skrull's unchecked presence on Earth could indicate the beginning of the alien race's surreptitious maneuvering.
There’s no reason to believe this unnamed character has malevolent intentions, but it’s also important to note the events of the film take place more than two decades before the modern MCU - and a lot can happen over all that time.
It takes the Skrulls of Marvel Comics a while to figure out how to shapeshift well enough to fool Earth's greatest minds - people like Reed Richards and Tony Stark - but the MCU version of the aliens appears to have already mastered the art.
Throughout Captain Marvel, Talos and his fellow refugees demonstrate the ability to mimic individual humans down to the genetic level. This means they’re already primed to occupy Earth should they decide to do so.
Kevin Feige is the president of Marvel Studios, but he might be more accurately described as the godfather of the Marvel Cinematic Universe. Feige is responsible for the overall vision of the MCU, and as such, he’s the most authoritative voice on the franchise’s future - and he hasn't ruled out Secret Invasion.
After being asked whether the events of Captain Marvel closed the door, Feige told Slash Film, "I don’t think it means that at all. I think it means that the Skrulls are as diverse and as multilayered as any other intelligent life form. Certainly like humanity itself. And we happen to see good ones. I think there are probably better ones out there as well, like there are with any fully realized characters. But yes, the idea certainly was to subvert the expectation of the pointy-eared green aliens."
It might be hard to imagine Talos and his friendly band of refugee Skrulls taking over Earth, but the Skrull population extends far beyond Mar-Vell's stowaways. The Skrull Empire has many factions, and each carries its own set of morals and motivations.
In the comics, the Skrull intrusion onto Earth is perpetrated by a religious offshoot of the empire led by a renegade Skrull queen who believes in a sacred prophecy regarding the planet. In other words, a similar conflict in the MCU would only take a few bad Skrulls.