Evangeline Lilly knew she’d eventually fly as the Wasp. But equal billing in the “Ant-Man” sequel?

That was a surprise.

“I knew [Hope Van Dyne] would get the suit at the end of the first film, and I was obviously very jazzed about that,” says Lilly by phone. “But we didn’t know if [a sequel] would come to pass.”

Lilly, 38, calls 2015’s irreverent “Ant-Man” origin story “a happy little success,” earning $180 million — a modest take compared with the gigantic hauls of films such as this year’s “Black Panther” ($699 million) and 2014’s “Guardians of the Galaxy” ($333 million).

So when they were a month or so away from shooting the sequel, Lilly got a shock. “I got sent a PDF photo in an email of the [double-billed] title card. And that’s how I found out.”

What’s more surprising, frankly, is that Lilly is even in the Marvel Cinematic Universe. Stung by the intense spotlight that came with fame after her run as Kate Austen on TV’s “Lost,” the actress famously declared an early retirement from acting in 2011.

Lilly never lived in Los Angeles; she was raised in British Columbia, Canada, and launched her career by taking bit parts in Vancouver while attending college. In the post-“Lost” years, she has made a life in Hawaii with her partner, Norman Kali, and their two children (now 2 and 7).

But the offers kept coming. Two years after going off the grid, Lilly got a call from Peter Jackson, offering a hard-to-pass-up passport to Middle-earth as an elf in his “Hobbit” films.

When Marvel dialed her up, “I realized, ‘You know what, this might keep happening,’ ” she says. “There is a very good chance I will be fortunate enough to continue to be given these opportunities to do these big films and to be in the spotlight. And I either need to draw a hard and fast line in the sand right now and say ‘I’m out and I’m never doing this again, no matter how cool the project is that comes along’ — or I just need to make my peace with it.”

Lilly chose the latter, and her entire stance on fame has shifted. Yes, Lilly is still private (the actress continues to live in Hawaii when not working) but today she’s less guarded, more willing to engage with fans on social media.

On Instagram, she speaks openly about everything from her politics to how she eats and works out to get her superhero body.

“I want to demystify stuff,” she says. “Something I really want to get out there, especially for young women: I’m wearing a corset under that [Wasp] suit. It’s really important to me that I point out to young women that it’s fantasy, it’s fun and it’s an ideal, but, like, my waist isn’t that teeny-tiny. I don’t have a Waspy waist.”