'House of the Dragon' director reveals how they swapped out an actor in the season finale without anyone noticing

• Warning: Major spoilers ahead for the "House of the Dragon" season one finale.
• Among the cast of the HBO show are Luke and Elliot Tittensor, who play the Cargyll twins.

When illness struck the set of "House of the Dragon" at the final hour, HBO counted its blessings knowing it had cast a set of twins.

Speaking on Entertainment Weekly's West of Westeros podcast, director Greg Yaitanes revealed exactly how they managed to avoid delays in shooting the season finale after the actor who plays one of the Cargyll twins caught COVID-19. Luke and Elliot Tittensor, 33, portray Arryk and Erryk, respectively.

After Elliot contracted COVID-19 on the second day of filming the finale, Yaitanes said Luke stepped up to fill in his shoes during a critical moment in the episode. The scene involved the return of Corlys Velaryon (played by Steve Toussaint) to Dragonstone before Ser Erryk informs Rhaenyra Targaryen (played by Emma D'Arcy) and her council that Otto Hightower (played by Rhys Ifans) arrived to negotiate terms.

"There's that scene, that big scene where Corlys comes down and they're putting the markers on the table and the messenger comes in," Yaitanes said on the podcast. He said the scene took over two days to shoot, during which Elliot, one of the twins, tested positive for COVID-19.

"So we swapped him out with his brother," Yaitanes said.

The change was largely imperceptible – unless Yaitanes had revealed it, it's unlikely anyone would've noticed.

If they hadn't had access to an identical actor, Yaitanes said it could've spelled disaster as they were about to shoot D'Arcy's coverage and the character of Erryk stands close to them.

"It would've killed us," Yaitanes said.

Although the "House of the Dragon" crew managed to evade delay in that instant, they couldn't completely avoid COVID-19 throughout filming in 2021. According to Radio Times, production was halted for two days in July 2021 after a member of the crew tested positive.

But now that the season has fully aired, fans will have to hope there aren't any further delays on the upcoming second season, which may only start filming in 2023, co-creator and executive producer Ryan Condal told Variety.