The mission seems impossible: To take a beloved movie that is, to borrow its own words, practically perfect in every way, and make a sequel 54 years later that’s bracingly fresh while staying true to the spirit of the original.

In the case of “Mary Poppins Returns,” the sprightly and charming follow-up to Disney’s 1964 classic “Mary Poppins,” it takes a lot of musical-theater savvy, a few well-placed cameos and a star, Emily Blunt, who inhabits the title role as confidently as Julie Andrews did back in the day.

Director Rob Marshall (“Chicago,” “Into the Woods”) and screenwriter David Magee (“Life of Pi,” “Finding Neverland”) begin by reintroducing us to Jane and Michael Banks, the children whose letter brought Mary to turn-of-the-century London. It’s now the 1930s, during “the Great Slump,” and the Banks family is again in distress.

Jane (Emily Mortimer) is a labor activist, carrying on the social tradition of her suffragette mother. Michael (Ben Whishaw) gave up art for a job as a teller in Fidelity Fiduciary Bank, where his late father worked. Michael is a recent widower, struggling to make ends meet and raise his three children, Anabel (Pixie Davies), John (Nathanael Saleh) and Georgie (Joel Dawson). Now the Bankses are in arrears, unless they can find Father’s bank shares and pay off a loan against the house on 17 Cherry Tree Lane.

When Georgie finds Michael’s old kite, he takes it out to fly and almost gets carried away by the wind. In comes Jack (“Hamilton’s” Lin-Manuel Miranda), a lamplighter — and, we’re told, onetime protégé of Bert, the chimney sweep played by Dick Van Dyke in the original — who helps keep Georgie on the ground. When the wind dies down and the clouds part, what should they find on the other end of the kite string but Mary Poppins.

Why is she back? “Same thing that brought me the first time, to look after the Banks children,” she replies. When Anabel asks, “Us?”, Mary’s offhand response is, “Oh, yes, you too.” (The moment evokes the 2013 movie “Saving Mr. Banks,” which chronicled the battle of wills between Walt Disney and author P.L. Travers — and Travers’ firm opinion that Mary came to rescue the father, Mr. Banks, not Jane and Michael.)

Mary sees immediately that Anabel, John and Georgie have had to grow up too quickly and sets about to remind them of the joys of childlike imagination. Bathtime becomes an aquatic adventure, while a porcelain bowl invites a journey into an animated scene — rendered much in the style of the first movie’s chalk-drawing world.

Meanwhile, Michael and Jane are confronted with two harsh realities. One is the fear that the bank, now led by the treacherous Mr. Wilkins (Colin Firth), will foreclose on the house. The other is the realization that their own childhood adventures, which as adults they dismissed as fairy stories, might have actually happened.

The musical score, by Marc Shaiman and Scott Wittman (the team behind “Hairspray” and the “South Park” movie), is loaded with songs that, while new, fill the spaces of the Sherman brothers’ classics. Miranda’s opener, “(Underneath the) Lovely London Sky,” is a scene-setter along the lines of “Chim Chim Cheree,” while Blunt’s first song, “Can You Imagine That?,” is this movie’s version of “Spoonful of Sugar,” and so on. Likewise, Meryl Streep’s turn as the eccentric Topsy, and her number “Turning Turtle,” evokes memories of Ed Wynn’s Uncle Albert singing “I Love to Laugh” from the ceiling.

The color palette is bright and colorful, as Marshall’s team borrows from the legendary matte paintings of Peter Ellenshaw to create its postcard-pretty London views. Not everything is a trapped-in-amber copy of the original, as shown by the choreography of Jack’s lamplighter colleagues performing parkour tricks and bicycle jumps.

The cast is up for anything. Mortimer and Whishaw bring the first movie’s Banks children into adulthood with flashes of their childlike wonder intact. Miranda is having a ball with his Cockney-inflected character, and his charm makes the romantic subplot between Jack and Jane less grating. And there are a couple of cameos toward the end — I won’t reveal spoilers, even if Disney’s marketing has — that will make audiences smile.

Best of all is Blunt, who’s a pro with musicals (she was brilliant as the Baker’s Wife in “Into the Woods”) and knows exactly how to deploy Mary’s prim and proper demeanor. Blunt’s Mary is a bit more standoffish than Andrews’ was, but her practical attitude toward even the most fantastical things is a necessary shield against overt sentimentality.

“Mary Poppins Returns” is a top-to-bottom delightful movie that will please fans of the 1964 movie and newcomers seeking a break from cynicism. Mary, once again, is just what this weary world needs.

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★★★½

‘Mary Poppins Returns’

P.L. Travers’ no-nonsense nanny returns to aid the Banks family in a movie that perfectly complements the 1964 original.

  • Where • Theaters everywhere
  • When • Opens Wednesday, Dec. 19
  • Rated • PG for some mild thematic elements and brief action
  • Running time • 130 minutes