Best known for playing the young version of Princess Rhaenyra Targaryen in season 1 of the hit Game of Thrones spin-off series House of the Dragon, Alcock also recently made her London theater debut in the National Theatre revival of The Crucible. Until now she has only appeared in one film, 2018 psychological horror The School, but that will all change with this role.
That's because Alcock's Supergirl is due to appear in 2025's Superman: Legacy, alongside David Corenswet's Superman. Then she will helm her own solo movie Supergirl: Woman of Tomorrow, which is based on Tom King's fan-favorite comic book series of the same name. And surely that's just the start – there will be more to come as Gunn and Peter Safran's DCU continues.
Intriguingly one of the actors Alcock beat to the role was Meg Donnelly, who has been the voice of Supergirl in several DC animated projects, including Crisis on Infinite Earths. Emilia Jones, the star of the Oscar-winning movie CODA, was also reportedly in the mix.
However, according to Gunn himself Alcock was the perfect choice for the role, writing on Instagram: "Milly is a fantastically talented young actor, and I’m incredibly excited about her being a part of the DCU. Yes, I first became aware of her in House of the Dragon but I was blown away by her varied auditions and screen tests for Supergirl."
Gunn then replied to comic book writer Jim Lee, who had commented on the filmmaker's Instagram post congratulating the DCU team on the news. Continuing to praise Alcock, Gunn teased: "I have to show you the test at some point, you’re gonna freak out." He's clearly thrilled by the casting.
And right now fans couldn't agree more, taking to social media to express their excitement. One user tweeted: "The more I think about Milly Alcock playing Supergirl the more I love it. This is gonna be so good you guys I can’t wait." Meanwhile, another stated: "Milly was the clear winner here and I am sure she will do an amazing job!"
For all the latest on the DCU plans, check out our guide to new superhero movies.