The Banks Family is in distress. The family nanny has just quit, and the two kids, Jane and Michael, have run away from home (though they actually just got lost chasing a kite). Their uptight dad, George Banks, decides to put out an ad for a strict no-nonsense nanny. But the kids write their own ad,
calling for a sweet and fun nanny. George tears this up and chucks it in the fireplace. But it gets blown up the chimney, and Mary Poppins magically gets a hold of it.
Even though Mary has a weird habit of reassembling thrown out garbage (like the ad), she's a nice person with magical powers. She arrives at the Banks house, zooming in on her flying umbrella as the wind blows George's strict nannies away. Flabbergasted, George has no choice but to hire her. She immediately astonishes Jane and Michael with her magical hijinks—helping them clean the nursery with magic that makes the nursery clean itself up. She also teaches them—and the rest of the world—that "A spoonful of sugar helps the medicine go down."