'The Big Bang Theory' Protagonist Returns for Spin-Off; Learn More

Another protagonist from the original series The Big Bang Theory is back in Stuart Fails to Save the Universe. After Raj’s return in the premiere episode, the second chapter of the HBO Max spin-off brings Kaley Cuoco back as Penny. In the new story, the character appears in an alternate reality leading a resistance group fighting against a regime dominated by artificial intelligence, alongside Zack, played by Brian Thomas Smith.

Her appearance comes after Stuart, Bert, and Kripke get trapped in that universe and end up being sent to a reeducation camp. After being freed, they are rescued by the resistance led by Penny, who believes the trio holds the key to defeating the AI. In practice, the group is only carrying the quantum interference device created by Leonard, Sheldon, and Howard, which allows travel between parallel universes. At the end of the episode, they escape with Denise’s AI version and head to a new reality where magic exists and scientists are persecuted.

The episode also marks the return of Ramona Nowitzki, played by Riki Lindhome, while Christine Baranski makes a special appearance playing herself in a video shown to the protagonists. The series has been expanding its connections to The Big Bang Theory by bringing back classic characters in different versions across the multiverse. Check out the full list here of every TBBT character who appears in the spinoff.

Episodes of Stuart Fails to Save the Universe are released weekly on HBO Max on Thursdays through September 24.