Stuart Fails To Save The Universe Brings Back Fourth Big Bang Theory Cast Member As Stuart's Shrink In Episode 4

"Stuart Fails to Save the Universe" welcomes its fourth "Big Bang Theory" cast member in as many episodes — following Kunal Nayyar as Raj in Episode 1, Kaley Cuoco as Penny in Episode 2, and Melissa Rauch as Bernadette in Episode 3 — when Mayim Bialik makes her franchise return in Episode 4.

Dr. Amy Farrah Fowler is the in-house therapist at the psychiatric ward where Stuart Bloom finds himself in this week's alternate universe, which is part "One Flew Over the Cuckoo's Nest," part "Pleasantville."

Given her real-life doctorate in neuroscience, co-creator Bill Prady says Bialik was an especially fitting choice to play Stuart's shrink. Plus, "her podcast that she's doing now is practically just therapy online," he says, referring to "Mayim Bialik's Breakdown." "And man, oh man, was she fantastic in those scenes."

Mayim Bialik joined "The Big Bang Theory," first as a guest star, in Season 3's finale, when Howard and Raj made Jim Parsons' Sheldon Cooper a dating profile that matched him with Bialik's Dr. Amy Farrah Fowler. Bialik was elevated to series-regular status early in Season 4, and would go on to appear in 203 (out of 279) episodes, with Amy and Sheldon marrying in Season 11.

But Bialik's stint as Dr. Fowler didn't end with "Big Bang." She'd go on to lend her voice to a pair of "Young Sheldon" episodes (Season 4, Episode 1, and Season 5, Episode 7), before returning in the flesh, opposite Parsons, in the prequel series' 2024 finale, which flashed forward to the near-ish future and revealed that Sheldon had been writing his memoir all along — hence Parsons' role as narrator throughout the prequel's 141-episode run.

The finale also offered a glimpse at Sheldon and Amy's life after "Big Bang": They were still living in Pasadena and raising two children — son Leonard, who played hockey for the Pasadena Penguins, and a daughter whose name was not revealed, but who had developed an interest in acting after Penny babysat her.

Now, two years later, Bialik is back as Amy once again — albeit as an alternate-universe version of the neurobiologist who traded the lab for a psychiatric ward.

Someone has been trying to get in touch with Stuart — possibly from the original "Big Bang Theory" timeline. In Episode 3's magic realm, Stuart and Kripke wandered right past a newspaper whose front page read, "Hey, Stuart Bloom!" And in Episode 4, upon Stuart's return home with Denise, it's his welcome mat that urges him to "wake up." 

Plus, Stuart Prime, making his first appearance since the premiere, leaves behind a comic book for his alternate self to find — and wouldn't you know, it's called "Stuart Fails to Save the Universe." Trippy!

Its contents reveal how Stuart broke the quantum entanglement device built by Leonard, Sheldon, and Howard: He stopped by Caltech to share the news of a clean colonoscopy, accidentally knocked the device off the table, and brought about a multiverse Armageddon that entangled him in the fate of the universe. The comic also provides instructions for ordering a new device, allowing him, Denise, Bert, and Kripke to escape this realm and transport themselves to the next. They land briefly in a "Matrix"-like reality before ultimately crash-landing in what appears to be a prehistoric one, setting the stage for Episode 5 — and the midway point of Season 1.