Milly Alcock on Supergirl’s darker edge and secret 'House of the Dragon' set guest

Milly Alcock snuck Fabien Frankel on 'Supergirl' set and he pretended to be from the make-up team to avoid attention

Milly Alcock has opened up about bringing a darker and more emotionally complex version of Supergirl to the big screen, while also sharing a humorous behind-the-scenes story involving her former House of the Dragon co-star Fabien Frankel.

The Australian actress stars as Kara Zor-El in DC Studios’ upcoming Supergirl, which is inspired by the acclaimed Supergirl: Woman of Tomorrow comic series. Unlike previous portrayals of the character, Alcock said this version of Kara is “messy”, flawed and still grappling with deep personal trauma following the destruction of Krypton. She believes audiences will connect with a superhero who reflects real struggles rather than an idealised image of perfection.

Directed by Craig Gillespie, the film follows Supergirl on an intergalactic journey alongside Ruthye Marye Knoll, played by Eve Ridley, as they pursue the villain Krem, portrayed by Matthias Schoenaerts. The story explores themes of grief, revenge and identity while maintaining a darker tone than many previous DC superhero films.

Alcock also revealed that she secretly brought her House of the Dragon co-star Fabien Frankel onto the Supergirl set during filming at Leavesden Studios. According to the actress, Frankel pretended to be a member of the make-up team to avoid attention, but became stuck on set when filming continued for around 20 minutes without a cut. “He almost got in trouble,” Alcock recalled.

The actress credited her time on House of the Dragon with helping her prepare for the role, particularly when it came to learning Kryptonian dialogue. Having previously mastered High Valyrian for the HBO fantasy series, Alcock said the process of learning a fictional language felt familiar, although she found Kryptonian even more challenging.

Director Gillespie praised Alcock’s audition and ability to balance humour, pain and vulnerability, saying she brought exactly the emotional complexity needed for the character. The filmmaker also highlighted the physically demanding nature of the production, which involved extensive stunt work, wire sequences and large-scale action scenes.

Alcock first gained international recognition as young Rhaenyra Targaryen in the HBO fantasy drama House of the Dragon. Now, she is set to headline one of DC’s most anticipated films as Kara Zor-El takes centre stage in a story that promises a very different kind of superhero journey.

Supergirl arrives in cinemas on June 26, 2026.