“Captain America: Civil War” was packed to the brim with superheroes, but it seems like “Avengers: Infinity War” will have an even larger roster. Directors Joe and Anthony Russo said they’ll not only bring together existing Marvel Cinematic Universe (MCU) characters, but they’d also introduce some characters.

“I can’t get into too much detail about who we’re introducing, but these two movies are intended to be the culmination of everything that has happened in the MCU since the very first ‘Iron Man’ movie,” Anthony Russo told IGN. “In being a culmination, these movies are in some ways going to be an end to certain things, and in some ways, they're going to be the beginning of certain things.”

Of course, no exact names were revealed, but Anthony also explained that they weren’t introducing people for the sake of making the cast list longer. Any new characters will be essential to the story. “You have to have them, or they shouldn't be in the movie,” the director added.

So who could be introduced in “Avengers: Infinity War”? Well, there are a few possibilities.

Captain Marvel — This seems like the most obvious (and widely rumored) choice. After all, Brie Larson was just announced as Captain Marvel, nearly three years ahead of the movie’s release date. With her headlining film scheduled to come out between the third and fourth Avengers, it seems like a great time to introduce her in a way similar to how “Civil War” introduced Spider-Man (Tom Holland) and Black Panther (Chadwick Boseman).

Squirrel Girl — There aren’t any official plans to introduce this quirky character to the MCU, but there’s clearly interest in the character. A couple of actresses are even campaigning for the part. Anna Kendrick has thrown her hat into the ring and scored an endorsement from the Russo brothers. “Stranger Things” actress Shannon Purser is also very interested in playing the character.

An Inhuman — Marvel Studios President Kevin Feige maintains that “Inhumans” is expected to be added back to the Marvel slate eventually. With that in mind, the movie could easily introduce someone like Black Bolt or Medusa — if “Marvel’s Agents of S.H.I.E.L.D.” doesn’t already have dibs on them.

Wasp — Okay, we’ve met the woman behind the Wasp, Hope van Dyne (Evangeline Lilly), but no one has seen her in action as the superhero yet. Considering “Ant-Man and the Wasp” is scheduled to come out just a couple months after “Infinity War,” it’s entirely possible that Ant-Man (Paul Rudd) could bring her into the fold.

Whoever ends up joining “Avengers: Infinity War” will join an all-star cast. Vin Diesel, who voices Groot, confirmed on his Facebook page that the Guardians of the Galaxy will team up with the Avengers in the 2018 flick, and the Russo brothers have also teased that it’ll be their most ambitious MCU film yet.

“Avengers: Infinity War” is scheduled to hit theaters May 4, 2018.