If Dylan O'Brien has lent his drumming talents to Taylor Swift’s highly anticipated new album, “The Life of a Showgirl,” he’s keeping it under lock and key. “Oh, I can’t say!” he teased with a knowing smile during an intimate chat at the premiere of his latest indie film, “Twinless,” held Tuesday night at the Pacific Design Center in West Hollywood. His eyes sparkled with mischief as he repeated, “You know, I can’t say.”

O’Brien’s drumming previously graced the track “Snow on the Beach” from Swift’s 2022 album, “Midnights.” Reflecting on that moment, he said, “It was an all-time bucket-list experience for me — one of those surreal dreams you never imagine coming true.”

Their creative chemistry also shone in Swift’s emotionally charged short film, “All Too Well,” where O’Brien shared the screen with Taylor and Sadie Sink (“Stranger Things”), delivering a performance that lingered long after the credits rolled.

Despite their close collaboration, O’Brien insists he hasn’t pressed Swift for a sneak peek of her new album. “I respect the space,” he said softly, with the kind of reverence reserved for art and artists who’ve shaped your life.

In “Twinless,” a darkly humorous and unexpectedly moving film, O’Brien takes on a dual role as Roman and his late identical twin, Rocky — a character whose vibrant, unapologetic spirit is revealed through haunting flashbacks. Alongside James Sweeney, who plays Dennis, the two form an unlikely bond in a support group for those grieving the loss of a twin.

Recalling his first read of the script, O’Brien said, “I was like, ‘What the fuck is this?’ And then I just thought it was amazing.” He spoke with genuine admiration for Sweeney, saying, “I did my homework on him and realized he was incredibly talented. I was shocked — in the best way — that something this special even came near me.”

The project had been close to his heart for nearly five years before cameras finally rolled. “A lot happened over the years,” he reflected, his voice thick with emotion. “But it never lost its magic. Every year, I’d read it again and still think it was the best thing I’d come across. It just kept growing on me, like a second skin. I knew I had to do it.”

And then there was the mustache — the now-infamous centerpiece of his transformation into Rocky. With a mischievous grin, O’Brien joked, “I’ve been waiting to whip it out. I really have.”

Sweeney, who also wrote and directed the film, shared the behind-the-scenes process: “It was a gradual build — we wanted the thickness just right. Dylan was sending me photos the night before filming, layering it back piece by piece until we hit that perfect length.”

The mustache, it turns out, was entirely O’Brien’s idea. “Originally, we were talking about a mullet,” Sweeney revealed, “but we both felt that wasn’t quite the right direction. Dylan brought the mustache into the mix — and suddenly, Rocky felt real.”

From start to finish, “Twinless” is a labor of love, and on September 5, it will finally reach audiences, thanks to a distribution deal between Lionsgate and Roadside Attractions.

Below, take a look at exclusive photos from the “Twinless” premiere — a night that felt like the beginning of something unforgettable.