Amy, Bernadette and Penny have "become the female wolf pack from 'The Hangover,' " Melissa Rauch tells THR, while Mayim Bialik stresses the importance of being careful when it comes to developing Sheldon's "nerd hero."

The Big Bang Theory’s recent female infusion comes to a head Thursday when Amy goes on a date with Stuart, forcing Sheldon to explore what jealousy is and what it means when it comes to the nature of his relationship with his female counterpart.

For the show, however, the recent wave of girl time can be viewed in multiple ways, according to co-stars Mayim Bialik and Melissa Rauch, who play Amy Farrah Fowler and Bernadette Rostenkowski, respectively, on the CBS ratings winner.

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While Amy and Bernadette both provide ways in which to tell additional stories about Howard (Simon Helberg) and Sheldon (Emmy nominee Jim Parsons) – and more recently Raj (Kunal Nayyar) and Leonard (Emmy nominee Johnny Galecki) -- the additions also allow Big Bang to tell tales from various female points of view, Bialik and Rauch say.

“It’s a combination of showing both,” Rauch tells The Hollywood Reporter, noting that Bernadette was at first a vehicle to show that Howard wasn’t all about being a “sleazy player.” “He really is kind of a hopeless romantic and really just wants love. I think [Bernadette] has been a great device in that way but now we’re exploring relationships of just the girls and seeing how Amy’s learning from the two of them. At this point, it has evolved into exploring the female relationships as well as it just being a way to explore more story lines for the guys.”

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Bialik, who fittingly has a doctorate in neuroscience from UCLA, joined the show as a recurring foil for Parsons’ Sheldon late in Season 3 and was promoted early the following year, while Rauch entered the picture as a love interest for Howard midway through Season 3 and was promoted to regular around the same time as Bialik.

"I think my relationship with Jim's character is perhaps the most complicated; he's such a beloved character … and we're seeing a whole other side of Sheldon," Bialik tells THR, noting that the writers are careful to be consistent with Sheldon as to not scare its core male viewers away.

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"[Sheldon] is the person who defies the most things about popular culture, popular notions of culture, popular social mores,” she says of the character who takes a scientific approach to just about every aspect of life. “For someone like myself who grew up in comic book stores and grew up as a misfit, he’s the nerd hero. We have to be careful with this character and we can't make him fall prey to the things that normal mortals fall prey to. Howard can but Sheldon can't; we need to be very careful with the nerd hero. Leonard is trying to fit in and wants the pretty girl next door. Sheldon doesn't, so it's this dance we have to do."

The actress, who grew up playing the titular character – a reformed nerd of sorts -- on NBC’s Blossom, notes that Big Bang has to remain true to what the show is at its core: a sitcom about friends and the life they lead in comic book stores and their professional lives.

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“People don't want The Big Bang Theory to turn into Friends; they don't want it to turn into 90210 and it never will,” she says, noting that the fact that the characters are nerdy scientists is woven in to the crux of the show. “I think we have to be really careful that it doesn't become those kinds of permutations of relationships. Our writing and producing staff are doing a great job of giving people what they want, what they love and what they're comfortable with but also making everybody kind of go outside their comfort zone a little bit."

While Sheldon, Leonard, Howard and Raj have long provided the male nerd viewpoint -- it's easy to see how the quartet of science, comic book and video game geeks are friends -- the unlikely friendship between Penny, Amy and Bernadette offer the opportunity to tell stories about various forms of the female nerd.

“They’re kind of a mismatched group,” Rauch says, noting the writers have formed this “informal sorority” between the trio. “Normally when you see women on TV hanging out together you see what they have in common right off the bat whereas this is a very unlikely threesome who wouldn’t have necessarily been friends in high school. But it works now because these girls are at this place in life when you realize there are no cool kids judging to see who you’re spending time with.”

Bialik, whose socially stunted character is dressed almost head to toe in polyester attire that typically runs two sizes too big for her, notes that Amy and Bernadette allow the show to explore “two different brands of the female nerd: the one who’s wearing the fitted sweaters and the pretty eyelashes and then my character, who they’re really making a physical statement about what it means to be this kind of female.”

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"People have said to me that this is exactly what it's like to be that painfully out of touch and want so badly to fit in; it's tender,” she says, adding that she’d love to eventually do an “ugly duckling” episode. “A good sitcom can do that: Amy is always one move away from being completely desperate, which is part of the complexity of her relationship with these other girls -- she's desperate for them. As the wedding unfolds, we're going to start seeing a lot more of Bernadette asserting herself.”

With talk about the impending nuptials between Bernadette and Howard, Amy will continue to take great strides into developing into a more progressive woman as she learns from her new “besties” ahead of being tapped maid of honor, with Rauch noting that learning works both ways within the sorority.

"Amy is so far off from being able to handle normal situations, though she has her desire to learn,” she says. “Penny is so smooth by comparison yet has her own big bag of issues. Bernadette falls somewhere in between the two with her own brand of awkwardness. They end up complimenting each other pretty nicely in that regard.”

“I think the addition of the girls has been interesting because the writers have done such a seamless job of transitioning what works so well with the guys into female scenarios,” Rauch adds, noting positive responses she’s received about the portrayal of the lady geeks from female fans at Comic-Con. “People are people whether you’re in skinny jeans like Penny or layers of polyester like Amy. I think that’s what works so well with the ensemble on Big Bang Theory, even before Mayim and I were added: It’s just a group of friends who love each other’s brilliance, weirdness, sluttiness and all.”

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Meanwhile, Bialik also notes that the female subplot also provides an opportunity to see Kaley Cuoco’s Penny in a whole new dimension. "The show now gets to depict her as socially superior, whereas she's normally kind of a foil. It's a really interesting way to expand the life of a show that already had such a huge fan base," she says, noting that her addition has also served as a way to bring out new aspects of not only Sheldon but, as seen in a recent episode, Leonard as well.

Cuoco, whose next door neighbor Penny was Big Bang’s main female perspective for two-plus seasons, says the addition of Rauch and Bialik “has been a good change.” “That’s what’s so great about the show: you can take any of the characters and put them in a room together and it’s funny,” she tells THR.

As Howard and Bernadette’s relationship continues to march toward the altar, Rauch confesses while she’s helped her recovering wannabe womanizer other half evolve, there’s still one big step forward he needs to make: getting the good Jewish boy to move out of his (unseen) mother’s house.

“That’s something that if Bernadette could do, I think she may win the Nobel Peace Prize for that sooner than she would for her pharmaceutical findings,” she says with a laugh. “That’s a huge, huge challenge and one that should be studied very closely under a microscope.”

Meanwhile, there’s still the big question of whether or not viewers will be treated to Bernadette’s bachelorette party. “They’ve kind of become the female wolf pack from The Hangover, so hopefully [a potential bachelorette party] will be something even worse than tigers and Mike Tyson,” Rauch laughs. “With Amy overseeing it, maybe it’ll just be a harp concert and Amy will lend us some of her polyester pajamas or something. I’m sure what ever it is it’ll have Amy’s own brand of weirdness slapped all over it.”

Asked whether she’s worried about alienating the show’s core male fan base – the Emmy-nominated Big Bang did follow the male-skewing Two and a Half Men for its first three seasons – Bialik isn’t worried. “As long as you’ve got Kaley Cuoco, we’re still OK,” she chuckles.

Email: Lesley.Goldberg@thr.com; Twitter: @Snoodit