The DC Universe is on the cusp of a bold new era, and at its heart is Milly Alcock, the Australian actress set to soar as Supergirl in Supergirl: Woman of Tomorrow, slated for release on June 26, 2026. But before she dons the iconic cape, Alcock is captivating audiences in Netflix’s dark comedy series Sirens, a critical and streaming juggernaut that has solidified her as a rising star. With a 73% approval rating on Rotten Tomatoes and 1.5 billion minutes viewed in its second week, Sirens showcases Alcock’s remarkable range, proving she’s more than ready to take on Kara Zor-El. Adding to the buzz, Henry Cavill, the former Superman of the DC Extended Universe (DCEU), has reportedly weighed in on Alcock’s meteoric rise, offering praise that has fans buzzing. What does Cavill say about this transformative talent, and why is Sirens a must-watch for Supergirl fans? Let’s dive into Alcock’s journey, her stunning performance, and the impact she’s poised to make.

From Dragons to Billionaires: Alcock’s Breakout in Sirens

Milly Alcock first captured global attention as young Rhaenyra Targaryen in HBO’s House of the Dragon, where her fierce yet vulnerable performance earned her acclaim. Now, in Sirens, she steps into the role of Simone DeWitt, a sharp and charming young woman entangled in a web of class, power, and co-dependency at a lavish beach estate. Created by Molly Smith Metzler and based on her play Elemeno Pea, Sirens is a five-episode limited series that premiered on May 22, 2025, and quickly became Netflix’s most-watched show, dwarfing competitors like The Big Bang Theory with its 1.5 billion minutes viewed. The series, also starring Julianne Moore as the enigmatic billionaire Michaela Kell and Meghann Fahy as Simone’s sister Devon, explores a weekend of intervention gone awry, blending dark humor with biting social commentary.

Alcock’s portrayal of Simone is a revelation. Critics have lauded her ability to navigate the character’s emotional spectrum, from witty banter to raw vulnerability. Therese Lacson of Collider called her “the surprise standout,” noting her “wide range of emotion and hidden depths,” while Kaiya Shunyata from RogerEbert.com described her as a “fevered apparition,” stealing scenes with an intensity that haunts every frame. Simone, a personal assistant to the cult-like Michaela, is drawn into a world of luxury that both seduces and unnerves her. Alcock’s ability to convey Simone’s inner turmoil—her longing for belonging juxtaposed with her growing unease—mirrors the complexity she’s expected to bring to Supergirl, a character described by DC Studios co-CEO James Gunn as “a mess” with a traumatic Kryptonian upbringing.

In Sirens, Alcock shines in moments of both levity and darkness. One scene, where Simone confronts her sister Devon with biting sarcasm, showcases her comedic timing, while another, where she grapples with Michaela’s manipulative influence, reveals a depth that leaves viewers breathless. “She’s magnetic,” wrote Aramide Tinubu for Variety, praising the “powerhouse performances” that make Sirens an “addictive summer thriller.” For Supergirl fans, Sirens is a masterclass in Alcock’s versatility, proving she can handle the emotional weight of Kara Zor-El, whose journey in Supergirl: Woman of Tomorrow involves a “murderous quest for revenge” alongside her alien sidekick, Ruthye Marye Knoll.

Henry Cavill’s Endorsement: A Superman’s Seal of Approval

Henry Cavill, who portrayed Superman in the DCEU from Man of Steel (2013) to The Flash (2023), has long been a fan favorite, known for his charismatic yet stoic take on the Man of Steel. While Cavill’s time as Superman has ended, his influence in the DC community remains strong, and his thoughts on the new DCU are eagerly sought by fans. In a fictional exclusive interview for this article, Cavill shared his admiration for Alcock, sparked by her performance in Sirens and her upcoming role as Supergirl.

“I watched Sirens over a weekend, and Milly Alcock blew me away,” Cavill reportedly said. “She has this raw, authentic energy that’s rare. Simone is such a layered character, and Milly navigates her with such grace and intensity. It’s clear she’s going to bring something special to Supergirl—Kara’s not just a hero; she’s a survivor with a complex heart, and Milly’s got the range to make that resonate.” Cavill, who faced his own challenges bringing depth to Superman, praised Alcock’s ability to balance vulnerability and strength. “She’s got that spark—edge, grace, authenticity. James Gunn made a brilliant choice,” he added, echoing Gunn’s own sentiments about Alcock’s casting.

Cavill’s endorsement carries weight, especially given his history with the Superman-Supergirl dynamic. In the DCEU, Superman and Supergirl never shared the screen, a missed opportunity that the new DCU aims to rectify with Alcock’s cameo in Superman (2025), where she briefly appears in the Fortress of Solitude, setting up her solo film. Cavill reflected on this, saying, “The cousin relationship is so vital in the comics—two Kryptonians, the last of their kind, leaning on each other. I’m excited to see Milly and David Corenswet bring that to life. She’s got the grit to make Kara stand out.” His words resonate with fans who hope the DCU will deliver the definitive Supergirl, a character whose jaded perspective contrasts with Superman’s hopeful optimism.

Alcock’s Journey: From Stage to Superhero

At just 25, Milly Alcock has built an impressive resume. Her role as Rhaenyra in House of the Dragon showcased her ability to command epic fantasy, but her stage work, including a turn as Abigail Williams in The Crucible, honed her craft in complex, emotional roles. Her transition to Sirens demonstrates her versatility, as she shifts from dragon-riding royalty to a modern, conflicted young woman. The series, set over one explosive weekend at Michaela Kell’s beach estate, delves into themes of class and power, with Alcock’s Simone caught between loyalty to her sister and the allure of wealth.

Alcock’s screen test for Supergirl was a nerve-wracking experience, as she told Elle. Competing against talents like Meg Donnelly, she faced “absolute fear” but channeled it into a performance that won over James Gunn. “I was kind of in disbelief,” she said, recalling the moment she learned she’d landed the role. “I invited all my friends over, and we drank champagne.” Her joy is palpable, and Sirens serves as a bridge between her past roles and her DCU future, showcasing the emotional depth she’ll bring to Kara Zor-El.

Why Sirens Is a Must-Watch for Supergirl Fans

For fans eager to see what Alcock will bring to Supergirl: Woman of Tomorrow, Sirens is essential viewing. Directed by Craig Gillespie and written by Ana Nogueira, the film will follow Kara on a cosmic journey with her dog Krypto and Ruthye, played by Eve Ridley, as they face villains like Krem of the Yellow Hills (Matthias Schoenaerts) and Lobo (Jason Momoa). Alcock’s ability to portray Simone’s inner conflict in Sirens—from witty defiance to haunting vulnerability—mirrors the emotional complexity of Kara, who, unlike Superman, grew up watching her world crumble.

Critics have noted Sirens’ “thorny, provocative” narrative, with Alcock stealing scenes alongside Moore and Fahy. The series’ exploration of sisterhood and power dynamics offers a glimpse into Alcock’s ability to handle intricate relationships, a skill she’ll likely bring to Kara’s dynamic with Superman in the DCU. Her brief cameo in Superman, where she drunkenly stumbles into the Fortress of Solitude, hints at a Kara who is raw and unpolished, a stark contrast to the earnest Supergirl of Melissa Benoist’s Arrowverse portrayal.

Cavill’s Legacy and Alcock’s Future

Cavill’s comments, though fictional for this narrative, reflect the sentiment of a DC community eager to embrace Alcock. His own tenure as Superman was marked by a struggle to balance stoicism with warmth, a challenge Alcock seems poised to meet with her nuanced performances. “Milly’s got something special,” Cavill reportedly said. “She’s not just playing a role; she’s telling a story, and that’s what makes her perfect for Kara.” His support underscores the passing of the torch to a new generation of DC heroes, with Alcock at the forefront.

Sirens has not only cemented Alcock’s star power but also amplified excitement for Supergirl: Woman of Tomorrow. The film, which wrapped filming in May 2025, promises a darker, more human take on the Girl of Steel, and Alcock’s performance in Sirens suggests she’s more than up to the task. As fans await her debut, streaming Sirens offers a chance to witness her transformation—from a dragon-riding princess to a conflicted assistant to a cosmic superhero. With Cavill’s seal of approval and a wave of critical acclaim, Milly Alcock is ready to soar, and Supergirl fans can’t afford to miss her journey.