It is that time in the life of a new musical comedy when the dance numbers become sharper, the scene transitions smoother, the funny moments land more crisply. Actors are "off book" — that is, no longer using their scripts. Now, too, they wear costume pieces as they run longer stretches of the show, in a high-rise Manhattan rehearsal studio with an imaginary stage outlined in tape on the floor, makeshift props on the tables, and members of the creative team following along on their laptops. 

At one of those computers sits one of the few people in the room who has never done anything like this before. Yes, live from New York, it's Tina Fey, in her Broadway debut — or at this point, her pre-Broadway debut — as the writer of one of the buzzier projects of the season: a musical version of the only movie she's ever written, the hit 2004 comedy "Mean Girls."

For a sense of how theatergoers react and what might need to be fixed in the show — scheduled for an official Broadway opening in April — "Mean Girls" is relying on Washington, D.C., audiences. The show's tryout run at the National Theatre begins previews today and has its formal opening night Nov. 19, when reviews will be posted. It's the latest in a long line of musicals that have stuck their toes into capital waters before taking a New York dive, a tradition represented recently by the Tony Award-winning blockbuster, "Dear Evan Hansen," born at Arena Stage, and "Come From Away," a Broadway success that had a crucial early stop at Ford's Theatre.

Along with her husband, Jeff Richmond, a longtime collaborator who composed the music, and Nell Benjamin ("Legally Blonde: The Musical"), who wrote the lyrics, Fey is attempting a feat that turns out to be a lot harder than it may sound: taking a movie people love and transforming it into a musical people will pay much moolah to see. Just ask the producers of the recently shuttered "Groundhog Day," a $17 million Broadway flop, how tough this can be.

Plus, it's a jampacked season for brand names in Broadway musicals: Disney's "Frozen," Jimmy Buffett's "Escape to Margaritaville," a SpongeBob SquarePants musical. And there's no telling whether the fans who made "Mean Girls" an international sensation more than a decade ago will post positive comments online about this venture - or consign it to the fraying pages of their old high school Burn Books.

You don't know what a Burn Book is?!? OMG, go watch the movie!

Like "Dear Evan Hansen" and "Come From Away," "Mean Girls" enters the Broadway sweepstakes without a star. The show's best-known player is Kerry Butler, who created the role of Penny Pingleton in the 2002 musical "Hairspray" and now plays the authority-figure characters assayed in the film by Fey and Amy Poehler. The young actresses who played the movie's high school heroine and villain — Lindsay Lohan and Rachel McAdams — are succeeded here by Erika Henningsen as conscientious but eager-to-fit-in Cady Heron, and Taylor Louderman, as vindictive leader of the pack Regina George. The hope, of course, is that these teenage-character assignments could be the kind of career-defining turns that, say, Evan Hansen has been for Ben Platt.

Easily the best-known person attached to the project is Fey herself, a comedy dynamo who achieved fame on "Saturday Night Live," went on to fill her shelves with Emmys for NBC's "30 Rock" and created, with Robert Carlock, the endearing Netflix sitcom gem "The Unbreakable Kimmy Schmidt."

"Mean Girls" has some promising things going for it, among them, wry source material with appeal for a younger market; a songwriting team that exhibits a natural affinity for Fey's original script; and a director-choreographer, Casey Nicholaw, who, courtesy of his work on "The Book of Mormon" and "Spamalot," has proved he knows how to stage songs that feed off the cleverness of premier comedy writers. In Fey, too, the production boasts the presence of a major talent who exhibits a level-headedness about an enterprise whose cost has been speculated to be in the neighborhood of $15 million.

"At 47, I feel like I know what I know, I know what I don't know, and the one thing I know that the four of us have that's very strong, is work ethic," Fey says of the creative team, during a lunch break. "And willingness to learn, and absence of rigidity. And all we can do is just keep working and checking and being vigilant and feel like we're doing the best version we can. And the other stuff beyond that is kind of out of your control."

It was the trust he had in Fey's instincts that persuaded Lorne Michaels, the "SNL" producer and her mentor, to produce the "Mean Girls" movie. And it was Michaels to whom Fey turned when she and Richmond decided to pursue a musical version of the film. Over the years, Fey and Richmond heard about unauthorized stage adaptations of "Mean Girls" at colleges and such: "I never saw any of them, but I remember thinking like, 'Hey man, you don't have permission to do that!'" Fey says. And with two girls of their own, now aged 12 and 6, they saw the commercial potential for this story on Broadway.

"It had solid characters and situations and timely issues," Richmond says, sitting with Fey, Benjamin and Nicholaw in a small conference room next to the studio. "We have girls now, and I see where this kind of property would mean more than it did 10 years ago. At least in our world."

Michaels, whose Broadway producing credits were limited to solo comedy shows by the late Gilda Radner and by another "SNL" alum, Colin Quinn, nevertheless signed on for one of the lead producing roles for "Mean Girls." Because, well, Tina.

"Tina has as good and as tough an eye as anyone," Michaels says, in a phone interview. "I'll go with her anywhere. There is no one I have a higher regard for. Just on a level of intelligence, and heart."

"Mean Girls" runs through Dec. 3 at the National Theatre, 1321 Pennsylvania Ave. NW, Washington, D.C. Tickets are $48-$118; thenationaldc.org, 1-800-514-3849.