Kaley Cuoco returns as alternate-universe Penny in HBO Max's "Stuart Fails to Save the Universe"

Kaley Cuoco appeared in the second episode of HBO Max's "Stuart Fails to Save the Universe," portraying an alternate-universe version of Penny, the former "Big Bang Theory" character. In this dystopian setting ruled by artificial intelligence, Penny leads a guerrilla resistance and confronts Stuart, played by Kevin Sussman, and his companions.

Series co-creator Chuck Lorre told People that the show’s multiverse premise allows familiar characters to reappear with different backstories, noting, "She’s still Penny, but she has an entirely different background. She never worked at the Cheesecake Factory, never met Leonard. She’s a leader of a revolutionary guerrilla group, and she’s not averse to violence."

Lorre added to Variety that such variations are intentional, saying the multiverse environment enables characters to recur as themselves but with new histories. The original sitcom aired from 2007 to 2019, reaching about 20 million weekly viewers at its peak. "Stuart Fails to Save the Universe," which premiered on July 23, centers on the side character Stuart and includes cameo appearances from other "Big Bang Theory" figures. Co-creator Zak Penn explained that the team sometimes inserted characters like Penny into the rebellion storyline for narrative effect.

The series is the third spinoff linked to "The Big Bang Theory," following "Young Sheldon" and the upcoming "Georgie & Mandy’s First Marriage," and is scheduled to air Thursdays at 9 p.m. on HBO Max.