Allison Williams and Christopher Walken Allison Williams and Christopher Walken

Magic is in the air on the Bethpage, Long Island, set of the upcoming production of Peter Pan Live! Make that magic realism. The show's titular lead, Allison Williams, is using a break in rehearsal to survey her surroundings. An ecstatic grin spreads across her face, making her nearly unrecognizable from Marnie, the guarded character she's played for the past three seasons on HBO's Girls. You can hardly blame her: The massive soundstage — where the two-hour event will be performed live on Dec. 4 — has been transformed into a Neverland tailor-made for the forever young.

Elsewhere on the premises are treasures like the Jolly Roger — the ship where Captain Hook (played by Christopher Walken) will terrorize Pan and the Darling children — reimagined in hyper-saturated colors made for high-definition TVs, as well as evidence of Lost Boys, Islanders, mermaids, and pirates. It's safe to say that, if J.M. Barrie — the Scotsman who, in the early 1900s, created the tale of the boy who doesn't want to grow up — were to land here today, he'd have his argyle socks blown off.

The endeavor comes on the heels of one helluva victory lap for NBC. This time last year, the network was speeding headlong into the unknown as it prepared The Sound of Music Live! — the first undertaking of its kind in half a century, produced by Neil Meron and Craig Zadan and starring country queen Carrie Underwood. Would enough people watch to justify the reported $9 million budget? The answer was yes. Nearly 22 million viewers tuned in. "Of course, you never go in hoping for failure, but that kind of success? It was shocking," says Meron. Within a week, they'd begun working on Round 2.

"Peter Pan was always at the forefront of our minds," says Meron. The version they landed on, featuring a script by Irene Mecchi (the Lion King movie) and four new songs in addition to the original Broadway score, aims for more depth and emotion while retaining the bones of the classic: A mischievous boy transports three children — Wendy, John, and Michael — from the window of their turn-of-the-century London home to a world of adventure and danger. But while last year's gamble to resuscitate a cherished property paid off, Peter Pan could be seen as less of a follow-up than a doubling-down. "These are not a bunch of Austrians standing around talking about Nazis," jokes Christian Borle, who played Max Dettweiler in The Sound of Music Live! and will take on the dual roles of patriarch George Darling and Hook's henchman Mr. Smee. "The scope here is much more ambitious."

That became particularly evident during the first run-through in early October. "This show is huge," says Zadan. "At minimum, it's twice as big as The Sound of Music." Adds Glenn Weiss, a veteran of the Emmy and Tony Awards who is directing along with Rob Ashford: "We've got a cast of nearly 50 across two soundstages, which have been purposefully designed as one immersive environment." The sets will be seen and shot from virtually every angle ("We want the audience to be leaning in, like they're on the journey with us," says Weiss), requiring precision and planning among cast and crew.

Not to mention a high level of physicality. "I have five musical numbers, and there's dancing in most of them," says Walken. "It's intense, and fencing is the hardest. I don't want to get whacked." To survive, Williams has become a master of the home remedy. "You name it, I've been doing it," she says. "I put honey and lemon in everything. I've learned 'ice before, heat after.' There were two weeks when I was sore every day from all the fighting and flying."

Oh, yes, the flying. "It's very precarious," says Zadan. "You could get tangled, the mechanisms could break, you could go up and not come down." Still, says Williams, "Flying is the best. The first time you're being lifted into the air, everyone has this same expression of joy." And despite the logistical headaches, there's no acing this show without it. "A lot of little things can be off and we'd still be fine," says Broadway star Kelli O'Hara (Mrs. Darling). "But the flying is big — we all want that magical moment to work."

Plenty is riding on whether this works. According to Bob Greenblatt, chairman of NBC Entertainment, "We're already thinking of live musicals as an annual tradition," he says. "We will see how Peter Pan goes over." (On deck: The Music Man.)

If cast and crew are feeling pressure, you'd never guess. "It's chicken cutlet day!" declares one dancer as lunch is called. When you're in a storybook brought to life with adrenaline and pixie dust, it's best to leave the worrying to the grown-ups.

Peter Pan Live! airs Thursday, Dec. 4 at 8/7c on NBC.

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