Actor/singer Lin-Manuel Miranda had his work cut out mastering the fancy footwork required for his role in Mary Poppins Returns because he isn't a great dancer.

The Hamilton creator and former star portrays lamplighter Jack alongside Emily Blunt as the magical nanny in the sequel to the 1964 classic, but despite his background in musical theatre, Miranda really had to focus on getting the choreography just right.

"I think the dancing was the most challenging aspect for me, because if you watch Hamilton carefully, there's a lot of incredible dancing in there, (but) (lead character Alexander) Hamilton does almost none of it. He's standing and he's got a lot of words to say," he confessed to The Associated Press.

Luckily, producer had given the stars a full nine weeks to rehearse for the dance sequences, and Miranda credits the rest of the cast and crew with helping him look good onscreen.

"What happens when you do that with the film company (cast and crew) is, they become a company. We were a company of actors together by the time we were starting this journey," he explained. "We all rehearsed together and that was formidable and made me feel at home."

Miranda also had to channel a "child-like innocence" to play Jack onscreen, and he drew inspiration from his four-year-old son Sebastian, who was two at the time of filming, to embody the chipper, upbeat character who "finds the light in any situation".

The star hadn't displayed those qualities on the stage or screen before Mary Poppins Returns, so he's thankful that director Rob Marshall trusted him to pull off the part.

"I make these movies because I think part of being an artist is being in touch with that inner child. That part of us that was drawing and painting and making stuff when we were kids," he said. "Some of us specialised on those, and some of us grow up, and I feel like I've never grown up in a real way."

Landing the role of Jack in the Disney blockbuster has been an amazing opportunity for Miranda, because he's never done a movie "on the scale" of Mary Poppins Returns, something he's particularly thrilled to be a part of because he was a big fan of the original, which starred Julie Andrews and Dick Van Dyke.

"You know, I grew up dancing along with those penguins in front of my TV like everybody else," Miranda recalled of trying to mimic Van Dyke's famous scene with animated penguins. "It's just a dream."

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