How House of the Dragon kept that surprise Harrenhal cameo a secret

Warning: This article contains spoilers from House of the Dragon season 2, episode 3.

The third episode of House of the Dragon season 2 delivered a surprise that shocked even Matt Smith's typically unbothered Prince Daemon Targaryen.

Daemon arrives at the eerie castle of Harrenhal to claim the ancestral roost of House Strong and establish a stronghold in the Riverlands — even if everyone ends up being super chill and not putting up a fight. Ever since his ancestor Aegon Targaryen blasted the fortress with dragon fire from his steed Balerion "the Black Dread" during the conquering of Westeros, rumors have swirled that the now-half-ruined towers are haunted. Daemon is plagued by visions and creepy sounds as soon as he steps foot on the grounds during that rain-drenched night.

One vision in particular sticks with him. He's visited by Rhaenyra Targaryen, but not his current wife, as played by Emma D'Arcy. Instead, he sees younger Rhaenyra by way of actress Milly Alcock. She appears to him while tending to the lifeless form of Aegon II's dead son Jaehaerys Targaryen, the babe Daemon's killers-for-hire Blood and Cheese murdered in the season 2 premiere.

Alcock, of course, was the first to portray Rhaenyra in her younger years on House of the Dragon, opposite Emily Carey as young Alicent Hightower for the first five episodes of season 1. D'Arcy and Olivia Cooke officially took over the lead roles in episode 6 when a time jump in the story took viewers to meet these characters in their adult years.

"It was very easy in terms of will," series co-creator Ryan Condal tells Entertainment Weekly of the splashy season 2 cameo. "We were excited about the prospect. Milly was eager to come back and everybody was excited to have her back."

Alcock has since landed the high-profile part of Supergirl and will appear in Warner Bros.' upcoming slate of DC superhero movies, beginning with next year's Superman, which is currently filming. "She's very busy, so it was a tricky thing to navigate around the schedule, but we essentially had her in for a couple of days right at the start of production," Condal says. "I think one of our greatest feats was keeping that a secret all the way through, given the fact that it happened right at the beginning."

Condal told press in 2022 that he didn't have plans to bring back either Alcock or Carey for House of the Dragon season 2, but was not "closing the door on anything." The cameo came from a desire to tell a haunted house story for Daemon at Harrenhal and confronting what terrifies him most.

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"Instead of warfare or dragons or images of horror, it was really more of him being haunted by these people who he had done wrong by in his past, particularly young Rhaenyra," Condal explains. "That's the girl who took his claim, not elder Rhaenyra, played by Emma D'Arcy. It's that version of Rhaenyra that removed him as the heir to the throne, and then was named heir and took his claim. As you'll see his story at Harrenhal unfold, there is an element of Daemon having to reckon with his past and choices that he's made and things that he's done."

New episodes of House of the Dragon season 2 drop on HBO and Max every Sunday at 9 p.m. ET/PT.