Lizzy Caplan considers the naked vulnerability of ‘Masters of Sex’

NEW YORK — Lizzy Caplan was a senior in high school when she first experienced the crushing disappointment that comes with life as an actress.

“We did ‘Much Ado About Nothing’ and ‘Romeo & Juliet.’ And of course I wanted to be Juliet, but I got cast as Beatrice,” which made her angry, she recalls over late-afternoon coffee in SoHo at the tail end of a week promoting her new Showtime series, “Masters of Sex.”

With the benefit of hindsight, however, Caplan is able to see the silver lining. “Thinking I knew what I wanted out of my career in high school is, like, so naive. Beatrice is a much better role. I mean, my God.”

PHOTOS: Images from ‘Masters of Sex’

Her high school drama teacher was clearly on to something. It’s hard to imagine Caplan, 31, who’s spent the last decade playing a string of latter-day Beatrices — sharp-tongued tomboys like Janis Ian in “Mean Girls” and Casey Klein in “Party Down” — as Juliet, the quintessential moony-eyed romantic.

Now, she’s earning rave critical notices as a character not even Shakespeare could have envisioned. In “Masters of Sex,” she plays Virginia Johnson, one half of the famed sex research duo Masters & Johnson, whose 1966 tome “Human Sexual Response” became an unlikely bestseller, shattered myths about the female orgasm and helped ignited the Sexual Revolution.

The drama, based on Thomas Maier’s 2009 book of the same name, opens in 1956, the year that Johnson, a twice-divorced single mother, was hired as a secretary for William Masters (Michael Sheen), then a prominent gynecologist at Washington University School of Medicine in St. Louis. Though she lacked medical training or even a college degree, Johnson quickly became an invaluable collaborator and, later, his wife.

As embodied by Caplan, Johnson is a woman well ahead of her time, at once sexually liberated and emotionally closed off.

“Everything she does is a series of contradictions,” says the actress, who, much to her disappointment, never got the chance to meet Johnson. The researcher died in July at age 88.

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Though Caplan would appear to have little in common with the farm-girl-turned-sexologist, she found it helpful to focus on their points of connection — such as, both she and Johnson lost their virginity to their high school sweethearts.

“It was just a completely appropriate, safe, lovely way to start experiencing myself as a woman. There was nothing traumatic. And that’s so luck of the draw, kind of terrifyingly so. I guess my dad is going to know how I lost my virginity,” she says, suddenly catching herself revealing a bit too much information.

Then, with a shrug, she continues: “But if I can’t have that conversation at this point, after this week, well …”

Caplan grew up in the heart of Los Angeles, on the Miracle Mile, but had what she describes as a “suburban upbringing”; the first time she ever visited a television or movie set was for a job.

“I’m really lucky to live in the town I grew up in, so if I’m sick of all this stuff I have an escape within the city,” she says, acknowledging she’s sad her future offspring will be denied the same experience. “They’ll be the children of an actress, and they’ll never know that other L.A. that I got to know for the first half of my life.”

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Caplan made her TV debut, as Jason Segel’s disco-loving girlfriend on the beloved “Freaks and Geeks,” while a teenager, but she was not the type who dreamt of stardom from a young age. Instead, acting was simply a way to stay in the performing arts program at Alexander Hamilton High School after she quit the piano in the 10th grade. (“It was easier than playing the piano,” Caplan says. “Like way, way easier.”)

Caplan’s mother died when she was 13, and the loss, she says, helped forge her tough-girl persona. “That was it: I was going to be the one who pretended everything was fine. I am tough, I guess, but I also know myself well enough now to know that true toughness comes from letting those walls down. It took me a long time to be able to do that.”

Friend Megan Mullally, who appeared opposite Caplan in “Party Down,” Starz’s cult sitcom about cater-waiters struggling to make it in Tinseltown, learned in their first scene together just how much the actress disliked getting touchy-feely: “Her character was so cool and not a person you would snuggle up to, so I thought it would be funny to really get in her space and just stand way too close and reveal way too much information. And it did really make Lizzy uncomfortable.”

But she also experienced Caplan’s sweeter side. One day, the actress surprised her with a landscape painting from a secondhand store. It’s “really, really cheesy” but also “kind of beautiful,” says Mullally, who brings the painting with her any time she’s on location. “I hardly ever get this, actually, but I had almost a maternal feeling toward her.”

Despite a vague resemblance to Zooey Deschanel — “we both sort of have bug eyes and bangs,” Caplan reluctantly concedes — she is the virtual antithesis of the Manic Pixie Dream Girl. Indeed, the Lizzy Caplan Type is so singular that, in an inspired bit of stunt casting, she even guest-starred in Season 1 of “New Girl” as Julia, an acerbic foil to Deschanel’s “adorkable” Jess.

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“Your whole thing with the cupcakes and the braking for birds and the ‘Bluebirds, come and help me dress in the morning,’” Julia sneered. “The big, beautiful eyes, like a scared baby. I’m sure that gets you out of all kinds of stuff.”

Caplan not only identified with the snarky, sexually confident and slightly intimidating characters she so often played, she also “felt a strange responsibility” to represent a type of woman so often relegated to the margins of pop culture.

“It was easy to convince myself that I could be happy doing just that over and over again in slightly different incarnations. Yet now, having the opportunity to do something different, I can’t believe I ever thought that,” she says.

When Caplan’s name came up in the casting process, creator and show runner Michelle Ashford and John Madden, who directed and executive produced the pilot episode, were intrigued but skeptical. “Lizzy is so incredibly contemporary. She just radiates that,” Ashford says.

And it’s true: In person, clad in skinny jeans, a T-shirt and scant makeup, Caplan looks like she was hatched in a lab in Williamsburg. It’s hard to imagine her on the Upper East Side, much less in 1950s Missouri.

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After an initial meeting at Chateau Marmont, Ashford and Madden were thoroughly charmed but not ready to commit. “We were thinking, ‘She’s lovely and she’s funny and drinks a good martini,’” Ashford remembers, “And she was at a point in her life where she just didn’t have to audition for TV roles. But we had to say, ‘We can’t just give you the part without you auditioning.”

It worked: Ashford and Madden were bowled over by Caplan’s tape. “The poor thing, they had really done up her hair and makeup in a way that was a little vampy,” Ashford says, “but there was something that shone through, her natural energy.”

Caplan, accustomed to the more improvisational world of comedy, is the first to admit that playing Johnson was a challenge. “All the things I thought were huge tools for making my characters believable were stripped away from me. I couldn’t say ‘Yeah’ and mumble and pad lines. I had to sit up straight and know the scripts word-perfect.”

The constraints, according to Ashford, “forced her to button up” in a way that, paradoxically, allowed that “incredible energy of hers to seep through.”

Her friend Nick Kroll, the actor and comedian, agrees: “She is a rare combination. She has the beauty of a leading lady, the comic timing of a stand-up, and the vulnerability of a supporting actress. So I think the combination of that leads to really textured performances, and ‘Masters of Sex’ is a great example of that.”

PHOTOS: Images from ‘Masters of Sex’

The part also required Caplan to get unbuttoned — frequently. She had already appeared nude for a guest role on “True Blood” in 2008, but in “Masters of Sex” Caplan strips down almost weekly, as does much of the cast.

Caplan recalls being filled with terror when, as the series was about to go into production, Ashford sent her an outline of the episodes ahead.

“I had a year away from the nudity [after filming the pilot]. And I just remember sitting at my kitchen table reading it all at once, being like, ‘Oh, my God, I have to do it.’ It was really overwhelming,” she says. “You have such mixed emotions about it, especially as a woman. It’s like, am I exploiting myself or am I empowering myself?”

The sense that she had “a real voice on the show and on set” helped Caplan feel at ease as did that “Masters of Sex,” unlike other premium cable dramas, doesn’t simply use the naked female body as set dressing.

“It’s a testament to the writing that you can have a show about sex with lots of female nudity and still have it be a feminist story,” she says.

Beatrice would approve.

meredith.blake@latimes.com