Given the tens of thousands of videos uploaded to YouTube every day, you can imagine how few of them make their way to Judd Apatow's browser.
But in late 2010, he happened to catch one mildly viral clip featuring actress Allison Williams. Titled "Mad Men Theme Song ... With a Twist," it features the then 21-year-old actress wearing nostalgic dress and opera gloves and singing the lyrics to "Nature Boy," while an abbreviated orchestra plays the signature tune to one of her favorite series. It was enough to make Apatow ensure that Williams see the pilot script he was producing.
Little more than a year and a half later, that pilot is Lena Dunham's Girls, premiering April 15 on HBO.
"I guess he saw something in my performance that kind of rung true with Marnie," Williams tells The Hollywood Reporter of her character, the most composed of the female foursome highlighted in the series. "I can kind of understand that now. There's a sort of cleanliness to it that's consistent with Marnie. He contacted [my agent] and said to make sure I got the script, which was a lot of pressure. Not only did I have to worry about disappointing myself, I might disappoint Judd Apatow."
She did not. Apatow and fellow EP Jenni Konner cast Williams as the roommate to creator Dunham's desperately confused lead.
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"It was the first thing that I really auditioned for after I moved to Los Angeles," says Williams. "I didn't expect that I would fall so in love with the first thing I read, but it felt so familiar to me. I thought, 'If I can't pull this off, I'm going to be heartbroken and watch every episode of the show ever, but I'm going to be so sad that I'm not going to be a part of it.' "
Getting the part of Marnie, an immaculately dressed gallery worker with a doting boyfriend who's passed his romantic expiration date, meant moving straight back to New York, where she was living after graduating from Yale University in 2010.
"It was very funny having to pack my stuff back up after very dramatically moving out there," she says. Williams is now back in New York, where Girls films and where she now finds her likeness plastered on subway platforms and billboards as a part of the series' expansive marketing campaign: "It's very weird waking around a corner and being nose to nose with myself on the side of a bus. And Times Square -- that's the craziest one. I'm really psyched it's above Walgreens, though. There's something poetic about that."
Fame, however new, is not something entirely foreign to Williams. She's the oldest child of NBC Nightly News anchor Brian Williams, whose regular presence in most American homes appears to have had little effect on his family.
"The weird thing about growing up with him is that I feel like he was so much my dad that it didn't occur to me that he was famous or well-known until I was old enough to pay attention," she says. "And by then I was old enough to realize that his is a very different kind of recognition. He's himself, every night, talking about very serious things. And for my life, I will be playing different people. ... I feel very lucky to not be blindsided by it. That said, there's really not anything that can prepare you for this -- and nothing has really even happened yet."
Well, not "nothing." Williams, Dunham and fellow stars Jemima Kirke and Zosia Mamet wrapped production on 10 episodes of the freshman season. And before its premiere, the praise has been fairly unanimous. THR critic Tim Goodman wrote that the first three episodes "convey real female friendships, the angst of emerging adulthood, nuanced relationships, sexuality, self-esteem, body image, intimacy in a tech-savvy world that promotes distance, the bloodlust of surviving New York on very little money and the modern parenting of entitled children, among many other things - all laced together with humor and poignancy."
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"I think what's wonderful is that in your early 20s, there's no such thing as perspective," Williams says of Girls, noting the series' creator, star and director might be an exception. "The amazing thing about Lena is that she seems to have third eye, this maturity and wherewithal to be able to look at her own life and relate it to the broader experience. I think she's almost uniquely suited to this because she's able to comment on her life as it's happening, which is very rare."
And for anyone who isn't yet familiar with Girls, Dunham's commentary includes a lot of sex. Williams has her own share of risqué moments throughout the course of the series, something she doesn't think will take hold of the dialogue.
"It was definitely a challenge for my first time out of the gate, but [Dunham] cultivated such a professional atmosphere that I felt totally comfortable," she says. "And she goes so far above what she asks of us; it feels right to fall in line."
Given the good buzz and HBO's fondness for renewals, Williams can expect to toe that line for some time to come -- the only negative being a DVR conflict between her new series and Sunday time-slot neighbor Mad Men.
"I've gotten so used to hearing the song with 'Nature Boy' in it," says Williams, laughing. "Every week when I watch the show now, I half-expect Jon Hamm to start singing."
Girls premieres at 10:30 p.m. Sunday, April 15.
Email: Michael.OConnell@THR.com; Twitter: @MikeyLikesTV