HBO’s Stuart Fails to Save the Universe is an upcoming science-fiction comedy television series that expands the universe of The Big Bang Theory, boldly going where no former cast member has gone before: the realm of science-fiction, action-adventure.
The series follows comic book store owner Stuart Bloom (Kevin Sussman) as he becomes entangled in a multiverse-spanning adventure with side characters geologist Bert Kibbler (Brian Posehn), comic book expert Denise (Lauren Lapkus), and plasma physicist, string theorist, and overall jerk Barry Kripke (John Ross Bowie). In the series, the crew goes on a dimension-hopping quest to restore reality, encountering chaotic alternate-universe versions of beloved characters from the original series along the way.
All of the characters appeared on The Big Bang Theory, which ran for 12 seasons on CBS from 2007 to 2019. Chuck Lorre and his Big Bang Theory partner, Bill Prady, serve as cocreators on Stuart Fails to Save the Universe along with Zak Penn.
So, that raises the question: which legacy characters will they encounter as they travel through the multiverses?
Here is a look at who we know is returning, a few veiled hints, and a few well-worded wishes. Please enjoy.
Stuart Fails to Save the Universe, Series Premiere, Thursday, July 23, 9/8c, HBO Max
Sheldon Cooper
Jim Parsons‘ exact involvement as Sheldon Cooper has not been officially confirmed, though cocreator Chuck Lorre heavily teased the return of original cast members.
“That is a closely guarded piece of information,” Lorre said in an interview with TVLine published on July 28, 2025.
Lorre was then asked if legacy characters would appear in Stuart Fails to Save the Universe — including Howard (Simon Helberg), Raj (Kunal Nayyar), Penny (Kaley Cuoco), Amy (Mayim Bialik), and Bernadette (Melissa Rauch). Lorre then teased, “You’re going to love this show.” So the possibility of Sheldon’s return is a strong maybe.
Leonard Hofstadter
“I cannot speak to that,” said Lorre in an interview. “That is a closely guarded piece of information that, you know… I’ve taken a blood oath regarding.”
Since the end of The Big Bang Theory, Johnny Galecki stepped away from Hollywood and now lives in Nashville, Tennessee. He relocated there from California and largely focuses on his family life with his wife, Morgan, and his children.
Penny Hofstadter
In an interview with Entertainment Tonight, Kaley Cuoco was asked if she would reprise Penny, and she all but confirmed with a pointed stare directly into the camera. “Big eyes!” said ET host Cassie DiLaura, “That’s not a no!” The actress shrugged and implied something was going on. “I love Penny,” said Cuoco. “It’s one of my favorite characters. It changed my life: professionally, personally. What a journey. I learned so much.”
Considering the actress just announced her second baby on the way, though, she might be a little tied up at the moment.
Howard Wolowitz
“There’s no plan for Howard to come back at the moment,” said Simon Helberg in a Screen Rant interview. While that may be disappointing news for Howard fans, it could also be Helberg being deliberately coy, as secrecy often surrounds surprise guest appearances. He previously reprised the role in Young Sheldon, so he is possibly open to returning to the character.
Raj Koothrappali
Kunal Nayyar hasn’t returned to the franchise since The Big Bang Theory ended, unlike several of his former costars who appeared on Young Sheldon. However, he remains one Stuart‘s biggest supporters, frequently congratulating the cast on social media.
While Nayyar has not been officially announced, his continued enthusiasm for the franchise makes a future appearance seem at least possible.
Amy Farrah Fowler
“I haven’t been contacted [to appear on it],” Mayim Bialik said in an interview. “I’ve seen what’s been announced, and I think that’s where a lot of people’s knowledge of it is right [now]. Me being one of them.”
Although Bialik has not been asked to star on the new project (yet?), she said she would be flattered if she were asked. “I love being known as that character,” she said. “I love what it means to people. So, for me, it would be a thrill to be part of it in any way.”
Bernadette Rostenkowski
Melissa Rauch has not been officially confirmed to appear on Stuart Fails to Save the Universe, but fans have been speculating she might appear in a cameo. Rauch has recently been doing press reflecting on her time as Bernadette. These well-timed media moments have fans in a tizzy that she is might be helping drum up buzz for Stuart Fails…
Wil Wheaton
Wheaton was spotted in the latest tease for the show; that is a definite yes. As the on-again, off-again frenemy of Sheldon Cooper (Parsons), Wil Wheaton famously played a heightened version of himself in the former CBS comedy.