Every Big Bang Theory cameo in Stuart Fails to Save the Universe, so far

In Episode 1, ‘Spoiler: Bert Dies,’ Stuart and the gang stumble upon a post-apocalyptic magic show led by illusionists Penn & Teller while searching for a device to save the universe. It’s a fun blink-and-you’ll-miss-it cameo with an extra treat for longtime The Big Bang Theory fans. Teller, who famously never speaks during performances, previously played Amy’s magic-loving father, Larry Fowler, on TBBT. This also marks his third different role across the franchise, after appearing as the dermatological entity Pus in Young Sheldon.

Episode 1 delivers its biggest surprise with the return of Kunal Nayyar as Raj Koothrappali. He’s one of the original Big Bang Theory gang. But this isn’t the Raj fans remember. He appears as a rugged alternate-universe version, complete with long hair and a beard, and is being held prisoner under Barry Kripke’s rule. Raj manages to crack the complicated math needed to fix the multiverse-breaking quantum device, only for Kripke to shoot him moments before he can reveal the solution. It’s a sad end for Raj, though only in this alternate reality.

Episode 2, ‘Spoiler: Zack’s in This One,’ drops Stuart and his friends into a dystopian alternate universe ruled by an authoritarian AI. Everyone is controlled through electronic devices implanted in their necks that shock them whenever they show “anti-social” behavior. After the trio breaks the rules, they’re arrested and forced to watch a re-education video for rebellious citizens. The surprise narrator and spokesperson is Christine Baranski, who plays herself. Longtime The Big Bang Theory fans will remember her as Dr. Beverly Hofstadter, Leonard’s mother, a role she played from 2009 to 2019.

Episode 2 also brings back Riki Lindhome, reprising her role as Ramona Nowitzki. In this alternate AI-controlled reality, she appears as a Caltech receptionist, where everyone is kept in line by microchips implanted in their brainstems. It’s an interesting twist on her original character from The Big Bang Theory. For those who need a refresher, Ramona was the physics graduate student whose over-the-top obsession with Sheldon Cooper made her one of the sitcom’s most memorable recurring characters.

And we also get to know why Episode 2 is titled ‘Spoiler: Zack’s in This One’. The spinoff brings back Brian Thomas Smith’s endearing goofball, Zack Johnson, in a surprising new way. Just when Stuart, Bert, and Barry think the worst is behind them after 30 months in the AI’s re-education program, Zack shows up and kidnaps them. In the original sitcom, Zack was Penny’s lovable but not-so-bright ex-boyfriend. The pair famously discovered they had unknowingly remained married for years after a drunken Las Vegas wedding.

Episode 2 doesn't make fans wait long for another big return as Kaley Cuoco reprises her role as Penny. In this alternate reality, Penny is leading the resistance against the AI overlord. Zack is working for her and carries out her orders to kidnap the trio. Believing Stuart, Bert, and Barry hold the secret to defeating the AI, she repeatedly slaps Stuart in an effort to deprogram him. When AI drones storm their hideout, the group is forced to flee and continue their multiverse adventure. In the Big Bang Theory, Penny was the warm-hearted neighbor who eventually married Leonard Hofstadter.

In Episode 3, titled ‘Spoiler: Bert Is Magic’, Stuart and his friends find themselves in a magical alternate universe. There, they discover that Bert is actually a wizard with magical powers, so the title makes sense. With Alexa's help, they learn about a “master sorceress,” who turns out to be Bernadette Rostenkowski (Melissa Rauch). She tells them that she has been banned by the Wizard Guild and needs the “blood of an innocent” to regain her powers. Stuart agrees, which turns out to be a big mistake, as she transforms into a 60-foot monster and creates mayhem all over Pasadena. Fortunately, Bert uses his own powers to get himself and his friends out of there. Rauch appeared in The Big Bang Theory from 2009 to 2019. She first joined as a recurring character before becoming a series regular. 

Fans may know Wil Wheaton from his run on the original sitcom, where he appeared in 17 episodes. In The Big Bang Theory, he played a slightly villainous version of himself. Now, he has returned for another cameo as himself, but with magical powers, in the spinoff. He plays a representative of the Wizards Guild of America. In Episode 3, he confronts Stuart for unleashing Bernadette, which eventually leads to a fight between Bert and Wil. The two destroy more than half of the comic book store, where Wil ultimately dies. 

Mayim Bialik made a cameo in Episode 4, titled 'Spoiler: Stuart Makes a Wallet'. She reprises her role as Amy Farrah Fowler, but with a fun multiverse makeover. While Stuart was confined in a mental health facility, he was assigned a psychiatrist who turned out to be none other than Amy. She thinks all the alternate universe stuff is not real, but simply a product of Stuart’s imagination, that’s all. Bialik joined TBBT in Season 3 as an intelligent but socially awkward neuroscientist, who eventually became Sheldon’s wife. Moreover, she even did voice acting for a couple of Young Sheldon episodes before starring in the prequel finale.

In Episode 4, Stuart experiences a vision where he sees himself at the top of a snow-covered mountain. There, he meets a Sherpa, played by Jon Cyler. He gives Stuart an absurd explanation about how he “converted” after meeting a woman online. Well, Cyler never really starred in the original show, but he was part of the cast of Two and a Half Men, created by Chuck Lorre, who also created TBBT. And if fans remember, Charlie Sheen from that show made a cameo in TBBT. So, this still counts as a cameo, in a way.

Parody songwriter ‘Weird Al’ Yankovic guest-stars as himself in the fourth episode of the spinoff. Stuart is having a drug-induced hallucination when he sees Yankovic in the room across the hall, pumping an accordion. Actually, Yankovic never physically appeared on TBBT, but he was mentioned in Season 7. Amy brought him up while making fun of Howard (Simon Helberg) for being a fanboy.