Beloved ‘Big Bang Theory’ alum makes wild return in ‘Stuart Fails to Save the Universe’ spinoff

Penny is back.

Kaley Cuoco reprised her “Big Bang Theory” role seven years after the hit show ended. 

Cuoco, 40, appeared in the second episode of the HBO Max spinoff series “Stuart Fails to Save the Universe” as an alternate-universe version of Penny, living in a dystopian world ruled by AI. 

In this version of reality, Penny is the leader of the resistance, who slaps Stuart (Kevin Sussman) and his friends. 

“I think at the end of the day, we handled some of those guest appearances beautifully in ways you don’t anticipate,” series co-creator Chuck Lorre told People on Thursday.

He noted that because “Stuart Fails to Save the Universe” takes place in a series of alternate realities, “Penny becomes someone else.

“She’s still Penny, but she has an entirely different background,” he noted. “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.”

In an interview published Thursday, Lorre assured Variety that it was part of the “design” of “Stuart Fails to Save the Universe.” 

Lorre noted, “In a multiverse environment, these characters could recur as themselves, but with an entirely different backstory.”

“The Big Bang Theory” originally aired from 2007 to 2019 for nearly 300 episodes. At its height, the sitcom drew 20 million weekly viewers.

On the main show, which followed a group of nerdy friends including Sheldon (Jim Parsons) and Leonard (Johnny Galecki), Penny was a waitress at The Cheesecake Factory and an aspiring actress who eventually married Leonard. 

On “Stuart Fails to Save the Universe,” which premiered July 23, Stuart (Sussman) – a side character in “The Big Bang Theory” – takes center stage. 

During a recent press conference held by the Television Critics Association, co-creator Zak Penn explained how “Stuart” wove in cameos by “The Big Bang Theory” characters. 

“Sometimes we would have an opportunity for a character and say, ‘Oh, the leader of the rebellion, that would be fun if that were Penny,’” he said. 

“Stuart Fails to Save the Universe” is the third “The Big Bang Theory” spinoff show, following “Young Sheldon” (which aired from 2017 to 2024) and “Georgie & Mandy’s First Marriage,” which is slated to premiere Season 3 on Oct. 8 on CBS. 

“Stuart Fails to Save the Universe” airs Thursdays at 9 p.m. on HBO Max.