Humor, heart, and a larger-than-life heroine: Sift those ingredients together with a lively original score, and the result is Mrs. Doubtfire, one of the most anticipated new musicals of the season. Adapted from the beloved 1993 film comedy, the show arrives at Broadway’s Stephen Sondheim Theatre March 9 after a sold-out extended holiday run in Seattle. Tony Award nominee Rob McClure steps into Robin Williams’s housedress as the titular nanny, alter ego of an unemployed actor desperate to spend time with his children in the wake of his divorce.

“This is the hardest thing I’ve ever done, but also the most thrilling and rewarding,” McClure says of his dual role, which involves 31 quick changes and a team of dressers. “When audiences first hear Mrs. Doubtfire’s Scottish brogue, they let out little gasps, which is so moving to me — there’s such an affection for the character.” Laughing, the actor adds, “No one would argue that it’s a good decision for a father to disguise himself as an elderly Scottish nanny, but in a funny way, that’s what it takes for him to learn what it means to be a good dad. He’s forced to see his family in a new light.”

McClure aims to honor Williams with his interpretation of Mrs. Doubtfire, as he honored Charlie Chaplin when playing the title role in the 2012 Broadway musical Chaplin, an astonishing performance that earned multiple award nominations. “My first responsibility is to let the audience know that I am just as big a fan of Robin as they are,” he says. “He was formative to my sense of humor and my heart, and I want to pay tribute to what he did. Once I establish that trust with the audience — once they see that I’m going to take care of this character — they give me permission to take her to new places.”

Having appeared on Broadway in musical adaptations of Beetlejuice and Honeymoon in Vegas, McClure explains that the key to a successful stage-to-screen transfer is finding moments that demand to be sung. “When the score springs from the emotional core of the story, that’s what makes a great musical,” he says, “and Mrs. Doubtfire has a profoundly moving emotional core. It’s not just a farce, although it is extremely funny. It also happens to be a beautiful family drama with emotional stakes from which the music can spring. Our team has found the right moments in the story for these characters to break into song, and that’s how we separate from the film and take off.”

Mrs. Doubtfire composers Wayne and Karey Kirkpatrick honed their skill at crafting clever, character-driven songs with their Tony-nominated score for the 2015 musical Something Rotten!. “They’re brilliant lyricists,” says McClure, “and Wayne, as a composer, wears his heart on his sleeve. He wrote [the Grammy-winning hit] ‘Change the World’ for Eric Clapton! That reflects his heart.” Karey Kirkpatrick and John O’Farrell’s book manages to be both hilarious and touching, expanding the roles of the three children and restoring moments that didn’t make it into the film.

“There a cut scene in which the teenage daughter is saying to the dad, ‘You’re an actor for a living, so why can’t you pretend you’re still in love with mom and not break up our family?’” McClure says. “It’s a lovely conversation that soars into song.” On the comedic side, the actor cites “Easy Peasy,” in which celebrity chefs emerge from Mrs. Doubtfire’s iPad when the hapless nanny is attempting to cook a dinner based on YouTube videos.

At the helm of the huge production is four-time Tony Award–winning director Jerry Zaks, whose Broadway credits span more than three decades, from Anything Goes with Patti LuPone to Hello, Dolly! with Bette Midler. “Want the audience to laugh? Get the guy who staged the original Lend Me a Tenor and the revival of A Funny Thing Happened on the Way to the Forum with Nathan Lane,” McClure says of Zaks. “He is the master.”

So far, no photos have emerged of the star in character as Mrs. Doubtfire, but he laughingly declares himself unrecognizable in the part. “The transformation has to be profound because he’s not just fooling strangers, he’s fooling his wife and children,” McClure says. “The audience will judge them if it’s not believable.” Seeing a bewigged nanny staring back at him in the mirror for the first time was a happy shock, compounded by the flabbergasted reaction of his costars at a photo shoot. “They were howling,” he says. “Everyone loved it.”

In conversation, McClure is warm and unpretentious, the product of a happy upbringing in suburban New Milford, New Jersey. He recalls falling for musicals when, at age 15, he was so shattered by a community theater production of Sweeney Todd that we went back the next day to see how a different audience responded. “I ended up going every weekend for three months — I was a Sweeney Todd superfan! — and the company gave me a cast jacket.” To this day, he enjoys watching an audience experiencing a show for the first time. “Sweeney Todd taught me that music can tell a story, and that’s what I love about musical theater,” he says, adding, “I cannot tell you how much it means to me that our show will open at the Stephen Sondheim Theatre.”

While Mrs. Doubtfire was in development, McClure and his wife of 10 years, actress Maggie Lakis, became the parents of daughter Sadie, now a year old. “Sadie spent her first birthday, first Thanksgiving, first Christmas, and first New Year’s in Seattle,” he says of the pre-Broadway engagement, “so we are raising a kid who is going to be nothing if not adaptable.” Coming to Mrs. Doubtfire as a new dad gave McClure insight into why a father might pretend to be a babysitter in order to see his kids. “The premise is extreme, but it explores the love between a parent and child in a way that I am just now fully understanding.”

When the show begins performances on Broadway, McClure looks forward to greeting families at the stage door, especially those touched by Mrs. Doubtfire’s expanded definition of a happy family. In Seattle, he says, “we had 5-year-olds and 95-year-olds all howling with laughter and then thanking us for exploring what family really means. They come to laugh, but they leave feeling very moved.” Personally speaking, the reward of starring in this dazzling new Broadway musical is simple: “It’s the most fun I have ever had on stage.”