The announcement at Comic-Con International that Captain Marvel will battle the Skrulls in her 2019 solo film left fans with many questions: Will the 1990s-set story delve into the Kree-Skrull War? Will the movie lay the groundwork for the Marvel Cinematic Universe's own Secret Invasion? And, perhaps most of all, how the heck does Marvel have film rights to the Skrulls, the shape-shifting aliens introduced in The Fantastic Four #2?

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Luckily, Guardians of the Galaxy director James Gunn is on hand to answer that last question. Again.

Responding to a fan who asked, "Skrulls are part of the MCU now?!!!" the filmmaker re-tweeted his answer from a year ago, explaining that Fox and Marvel Studios share the rights to those aliens. "Some specific Skrulls are at Fox," Gunn wrote in July 2016. "But the Skrulls as a whole are co-owned."

We've known since 2012 that some characters exist in a gray area that permits Fox and Marvel Studios to both use them on screeionsn, with some limitations. Most notably, Quicksilver was introduced in both Fox's X-Men: Days of Future Past and Marvel's Avengers: Age of Ultron (only to swiftly be killed off), and the Watchers -- an ancient alien race introduced in The Fantastic Four #13 -- cropped up this year in Guardians of the Galaxy Vol. 2.

“There are only a handful of characters that occupy that middle ground,” Marvel Studios President Kevin Feige originally explained in 2013. “Iron Man is not going to show up over there and Magneto is not going to show up over here. But there are a few gray points even after many years of negotiations … and that only happens with a character like Quicksilver, who has been a part of the X-Men, the son of Magneto in those comics, but also a primary Avenger.”

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Of the "some specific Skrulls" mentioned by Gunn last year, Super-Skrull is the most likely candidate firmly ensconced at Fox. Introduced in 1963 in The Fantastic Four #18, the original Super-Skrull, was re-engineered to possess powers that mirror those of Mister Fantastic, the Invisible Woman, the Human Torch and the Thing. Other Super-Skrulls have been introduced in Marvel comics over the years, but the original is the best-known by far.

Directed by Anna Boden and Ryan Fleck from a script by Nicole Perlman and Meg LeFauve, Captain Marvel stars Brie Larson as Carol Danvers and Samuel L. Jackson as Nick Fury. The film arrives March 8, 2019.