Penny leads a rebellion, Bernadette is a sorceress: every Big Bang Theory actor in the new spin-off

If you're wondering just how far Stuart Fails to Save the Universe has wandered from its sitcom roots, the answer is: about as far as a show can go without calling itself Doctor Who. HBO's spin-off has gone full-on sci-fi chaos—apocalyptic settings, sentient crystals, multiverse shenanigans—and with that, the doors have been flung open for all sorts of The Big Bang Theory alumni to pop in. Some play their old selves (sort of), others show up as completely new people, and frankly, the whole thing is a bit mad, but in a good way.

Right, so below I've gone through every significant Big Bang Theory actor who turns up in Stuart’s freshly doomed universe. Some are blink-and-you-miss-it cameos, some have entire storylines. A few are even playing three different versions of themselves in as many episodes. Here’s who makes the jump and what on earth they're up to this time.

Stuart Fails to Save the Universe features actors from The Big Bang Theory playing alternate versions of their old characters—and, in some cases, entirely new roles.

Main cast and big name returns

Let’s start with the regulars, then work outward. The main gang this season is:

• Kevin Sussman as Stuart (obviously)
• Lauren Lapkus as Denise
• John Ross Bowie as Kripke
• Brian Posehn as Bert

But what’s interesting is all the guest stars and cross-universe cameos. Here’s a rundown of the returning faces from The Big Bang Theory, plus the wild new twists their characters get in this universe:

Cameos, crossovers, and recasts

Kunal Nayyar is the first surprise: Raj Koothrappali pitches up in Episode 1, living in Bert’s old classroom and looking even more down-and-out than usual. Apparently, Raj got married after the TBBT finale… but, in classic Raj fashion, it was over almost before it started. He’s gone almost as soon as he arrives, but reappears in Episode 6, dishevelled and prophesying doom in the street. Blink and he’s back to square one.

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Kaley Cuoco returns as Penny—twice, no less. You’ll spot her leading a ragtag rebellion in Episode 2, then swinging back round as an army major in Episode 8. Neither universe comes with Leonard, but rest assured, she’s still up to her neck in random science fiction nonsense. Penny’s main job? Interrogating Stuart’s gang about a multiverse device. Sci-fi, but never far from her comfort zone.

Brian Thomas Smith's Zack Johnson—yes, Penny’s dim but lovable ex—turns up alongside Penny’s rebel forces in Episode 2. Not exactly a character evolution for Zack; he’s much the same old himbo, only now he’s somehow been put in charge of assisting Penny with an entire resistance movement. My money says she does most of the thinking.

Melissa Rauch pops up as Bernadette in two distinctly oddball roles. First, in Episode 3, she’s a dark sorceress conning Stuart out of his blood for her (literal) magical powers—worlds away from microbiology. Later, in Episode 7, she reverts to her competitive roots as a ruthless dance coach. Still recognisably Bernadette, just cranked up to eleven or run through a blender, depending on your mood.

Mayim Bialik gets two turns as Amy, both as almost entirely new people. Her first appearance—Episode 4—is as a therapist helping Stuart cope with reality falling apart. Then, twist time, she comes back in Episode 9, now married to Jay Garrick, aka the Golden Age Flash (no, really). New universe, new Amy, and she doesn't seem to recognise Stuart or the rest of the gang either time around.

Riki Lindhome manages three outings as Ramona Nowitzki in Episodes 2, 7, and 9. No more being Sheldon’s obsessive stalker; here, she’s a persistent thorn in the gang’s side, doing her best to block Stuart’s multiverse adventures at every step. If you wanted more chaos from the supporting cast, she delivers.

If you don’t remember Josh Brener from the main series, fair enough—he only showed up twice as Dale, Stuart’s mate from the comic shop. Here, he’s Trevor, a recurring customer who exists largely to get zapped, bungled, or otherwise caught up in the universe’s various messes.

Ryan Cartwright is the Kyle in the Trevor-Kyle double act and was previously Cole, Penny's British community college classmate, in TBBT. Here, he’s not just a one-off; Kyle gets plenty of screen time opposite Trevor for some increasingly comic misadventures.

Teller (yes, from Penn & Teller, rarely seen without Penn) cameos in Episode 1 as himself, wriggling through the apocalypse with his magical partner in tow. Both magicians play themselves in this universe, rather than any previous guest role from TBBT—though, if you remember, Teller was Amy’s dad Larry Fowler in the parent show, and the pair turned up in Young Sheldon as, of all things, a talking zit. It’s all getting very meta.

And finally, Christine Baranski—multiple-Emmy winner and, back in 2009, Emmy-nominated for her TBBT turn as Beverly Hofstadter—cameos not as Leonard's chilly mum, but as herself, kicking off Episode 2 with a training video intro. Your guess is as good as mine as to why, but somehow, her posh, clinical TV self isn’t a million miles away from Beverly anyway.

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