[This story contains spoilers for The Last of Us season one finale.]

Fans of The Last of Us video game got a special treat in the season finale of the title’s HBO adaptation: actress Ashley Johnson, who portrayed Ellie in the game, playing Ellie’s mother in the episode’s opening sequence. In a role unique to the show, Johnson’s character gave birth to Ellie just as she was bitten by Clicker, suggesting the cause of Ellie’s unique immunity to the Cordyceps infection.

“It does hint at and give some theories as to why Ellie immune, even though we don’t answer that conclusively,” notes creator and showrunner Neil Druckman.

“Ashley sounds like Ellie and Ellie sounds like Ashley,” showrunner Craig Mazin adds. “So she’s already like quasi-mythological creature to me. To see her giving birth to herself, in a sense, and to create that genetic connection between her performance as...