Three new actors have been added to the upcoming Big Bang Theory spin-off Stuart Fails to Save the Universe, which is in development at HBO Max.

According to Deadline, Ryan Cartwright (Kevin Can Wait), Josh Brener (Silicon Valley) and Tommy Walker (Henry Danger) are set for major recurring roles on the new show. Both Cartwright and Brener previously guest starred on The Big Bang Theory, although they'll be portraying new characters in the upcoming show.

The recurring trio join Big Bang Theory alumni Kevin Sussman, Lauren Lapkus, Brian Posehn and John Ross Bowie, who make up the series' main cast.

According to the show's logline, Stuart Fails to Save the Universe follows comic book store owner Stuart Bloom (Sussman) after he accidentally triggers a multiverse catastrophe by breaking a device created by Sheldon and Leonard. As he attempts to restore reality, Stuart is helped by his girlfriend Denise (Lapkus), geologist Bert (Posehn) and quantum physicist Barry Kripke (Bowie).

As the premise suggests, the series will introduce alternate-universe versions of familiar characters from The Big Bang Theory, potentially paving the way for guest appearances from original cast members.

As reported by Deadline, Cartwright will portray Kyle, a regular at Stuart's comic book store. Brener takes on the role of Trevor, while Walker plays Gary, Denise's handsome new boyfriend.

Ryan Cartwright, a British-born actor, is best known for his starring role on Kevin Can Wait and recurring appearances on Bones and Alphas. He guest starred on The Big Bang Theory as Cole, Penny's British study partner, in a Season 6 episode, and has since appeared in several Chuck Lorre sitcoms including Mom, Bob Hearts Abishola and B Positive.

Josh Brener is best known for his role as Nelson "Big Head" Bighetti on HBO's Silicon Valley, which ran for six seasons. He previously played Dale, an employee at Stuart's comic book store, in two episodes of The Big Bang Theory. His additional credits include guest spots on The Middle, Modern Family and The Neighborhood.

Tommy Walker is best known for portraying Drex Stinklebaum on Nickelodeon's Henry Danger and its spin-off Danger Force. He also guest starred in an episode of Chuck Lorre's Netflix comedy-drama The Kominsky Method.

Stuart Fails to Save the Universe was officially ordered by HBO Max in July, though it has been in development for a couple of years. The series comes from Big Bang Theory creators Chuck Lorre and Bill Prady, alongside The Avengers and Ready Player One screenwriter Zak Penn. A premiere date has not yet been announced.