Billie Eilish just made her surprise acting debut with a previously unannounced role in the wildly captivating Prime Video series, Swarm, from co-creators Donald Glover and showrunner Janine Nabers.

The singer, who appears in episode four, is just one of many unexpected supporting players who cross paths with Dominique Fishback. 

Now streaming, the series follows a young woman named Dre (Fishback) whose obsession with one of the world's biggest pop stars as well as an unexpected trauma involving her sister, Marissa (Chloe Bailey), sets her on a dark journey across the country. 

As Dre continues on her increasingly violent path, she encounters characters played by Damson Idris (Marissa's boyfriend, Khalid) as well as Bryron Bowers, Kiersey Clemons, Paris Jackson, internet personality Rickey Thompson, Rory Culkin and American Auto breakout X Mayo. 

That also includes Eilish, who plays Eva, a cult leader to white women played by the likes of Kate Lyn Sheil (House of Cards, The Idol) and others, who've all gathered together to attend the Bonnaroo Music and Arts Festival, which is being headlined by Ni'Jah.

Without giving too much away, Eva's encounter with Dre leads to a clashing of personalities before ending with bloody results.

While Eilish has appeared in several music documentaries and has voiced a version of herself for the Simpsons' short film, When Billie Met Lisa, Swarm marks the first time the singer is appearing in a fully scripted role. 

The idea to add her to the ensemble came from casting director Carmen Cuba, who knew that the singer wanted to get into acting. For Glover, casting Eilish, especially in addition to Bailey and Jackson, also provided an opportunity to play up the meta-commentary about fandoms and followers. 

When asked what Swarm might be saying about these stans, like the Beyhive, given the show's parallels to Beyoncé, Nabers told ET, "I think you can intellectualize it and say that it's a critique of fandom, of course."

"I created it with someone who is a music superstar, and I've seen people take ownership of him in real time, in real life, in front of my face. I think when you step outside, and you look at the story, is it a critique? Sure," she continued, referring to Glover, who has his own successful musical career in addition to producing and starring in TV projects like Atlanta.