'Peter Pan' star Allison Williams: Why she was born to play the boy who wouldn't grow up

"Losing your shadow: What is THAT about?" muses Allison Williams. "As a kid you just accept it. But as an adult, I've spent a lot of time thinking about what it means."

Williams, at 26 best-known for the HBO series "Girls," feels her life since childhood has pointed toward Thursday at 8 p.m. EST, when she (and her shadow) will headline NBC's "Peter Pan Live!"

As a toddler, she was already listening to the Broadway recording of "Peter Pan," and she viewed the 1960 NBC telecast starring Mary Martin countless times.

She even played Peter Pan with her grandparents.

"It was the only way they could get me into the bathtub," she recalls. "My grandmother would be Wendy, and she would take a toothpick and dental floss and pretend to sew my shadow on while I was splashing around. My father was Captain Hook. That was our game."

Soon after last November's triumphant live telecast of "The Sound of Music," NBC declared "Peter Pan" as this year's musical.

"From the second they announced it, I was emailing my agents constantly. I was sending them tapes of me singing 'Never Never Land.'"

Then she learned that Christopher Walken had been signed as the villainous pirate Captain Hook.

"I thought, 'What a cool choice!' And my desperation level went through the roof. Then finally the call came this summer: 'Would you like to do "Peter Pan"?'"

Here was a dream role that called for Williams to sing, dance, fight, master a British accent and, most challenging of all, fly.

"At first, to face a specific direction was hard. To land without looking down was hard. To maintain your body in a position where people don't see the harness was hard. Then you want to put your own personality into the flying style, to come up with tricks and positions that are original."

And working all this out, "you can't be up there too long at a time," she adds, "or you'll get sore. But it's soooo great. It's wickedly fun!"

It's as if she were born to be aloft in this role, and clearly she deems it a sacred trust, one about to come true, live, for an audience of millions.

"I will take very, very good care of Peter," she vows. "I promise. I promise."