Stuart Fails To Save The Universe Star Talks Kripke's Sexual Fluidity, Jokes Euphoria Would've Shown More Than Episode 5 Did

"Stuart Fails to Save the Universe" took its heroes to paradise in Episode 5 — and it didn't take them long to ruin it.

After crash-landing in a Garden of Eden-inspired universe — the first without an appearance by a "Big Bang Theory" legacy cast member, following previous cameos by Kunal Nayyar (Raj), Kaley Cuoco (Penny), Melissa Rauch (Bernadette), and Mayim Bialik (Amy) — Stuart, Denise, Bert, and Kripke find themselves welcomed into an idyllic community free of greed, jealousy, and traditional notions of ownership. But once the foursome begins introducing its inhabitants to such modern concepts as free-market economics and monogamy, paradise quickly starts to unravel.

"As much as Kripke is in trouble for introducing free market economics, introducing monogamy to that community doesn't go very well either," John Ross Bowie tells TVLine in the video interview above.

Brian Posehn, meanwhile, places some of the blame squarely on Bert. "Bert being a selfish lover probably ruins the whole place," he jokes. "By me going, 'No, you can only be intimate with me,' kind of ruins all of paradise."

"You pull that thread, and the whole sweater unravels pretty quickly," Bowie adds.

Monogamy isn't exactly a concept that comes naturally to Kripke, either. Episode 5 finds the Caltech physicist emerging from a yurt following a sexual encounter with both male and female partners, further establishing a side of the character first revealed in Episode 4, when an alternate-universe Kripke was shown happily married to his neighbor Gary (Tommy Walker).

"I think one of my favorite lines in the entire show is when the guy comes out of the yurt and I go, 'Hey, nice work in there,'" Bowie says. "Like, what just happened? I feel like if we were 'Euphoria,' we would have actually seen it. But yeah, that's fascinating."

Was Kripke's sexual fluidity something Bowie ever expected the "Big Bang Theory" spinoff to explore? "No, but I was thrilled to see it," he says. "As much as Kripke's a pig, I think he's so driven by his libido that he's not necessarily going to have a ton of hangups as to where he sows his oats. I loved it. There's a couple of references to sexuality existing on a continuum, and I was happy to be a part of that."

Bowie also recalls filming Kripke's Episode 4 scenes with Walker, revealing that director Kyle Newachek encouraged him to turn up the heat when Kripke kissed his husband.

"I do remember on the day where it is revealed I am married to Gary, I'm supposed to kiss him at the end of each scene, and they weren't getting what they wanted," Bowie recalls. "So Kyle Newachek, our director, comes over and goes, 'John, can you give him a really sexy one?' And that's when I like grabbed his chin and went in for it, and that's the one they used, and it looks great."

"And by the way, if you're going to kiss a guy, you could do far worse than Tommy Walker," he adds.

"He's a handsome dude," Posehn agrees.

While Kripke and Bert inadvertently introduce paradise to the pitfalls of monogamy, Denise — who never chose to accompany Stuart on his multiversal quest — is already nostalgic for the children they briefly shared in the previous reality.

"I think when we see them with their family, she's kind of a different version of herself, but then she remembers that in the next reality," Lauren Lapkus tells TVLine. "And so there is a twinge of, 'Oh, what if we had that? Or we almost had that. What was that?' And I think that just builds for their relationship. All these experiences just add to each other and give them more depth."

Lapkus also teases that those experiences will take on greater significance later in the season: "When we get to a future episode where it becomes even more real, they can kind of look at each other and go like, 'We've been through a lot together. And we even had fake kids at one point.'"

Kevin Sussman, meanwhile, likens their increasingly bizarre multiversal experiences to a particularly disastrous vacation. "Everything goes wrong and it sucks while you're there... but then when you come back, you have a stronger bond for having gone through it."

And whatever becomes of Stuart and Denise's relationship, their multiversal journey isn't ending anytime soon: HBO Max has already renewed "Stuart Fails to Save the Universe" for Season 2, with five more episodes still to come before Season 1 wraps on Thursday, September 24.