P.L. Travers so detested this film adaptation of her novel, she left the premiere in tears. Reportedly, she most objected to the altering of Mary Poppins' character from cold and intimidating in the novel to warm and cheery in the film. She also took issue with the film's perceived anti-feminist ending, in which Mrs. Banks gives up her campaigning for women's rights to stay at home as a housewife.
P.L. Travers wanted the animated chalk-drawing sequence removed from the film, but Walt Disney refused.
P.L. Travers was a stickler about details in the script, driving many of the Disney writers to distraction about Poppins minutiae. After seeing the final film, she devised a list of changes she wanted. Her requests went unheeded after Walt himself pointed out that although she had SCRIPT approval, she didn't have FINAL DRAFT approval. Among the things that she disliked was the Sherman Bros. score. She wanted the only music in the movie to be period pieces such as "Ta Ra Ra Boom De Ay" or "Greensleeves".
A sequence known as "The Magic Compass", consisting of four songs, was dropped from the film in preproduction. One of those songs, "The Beautiful Briny", later resurfaced in Bedknobs and Broomsticks. The melody for another song from this sequence, "The Land of Sand", was used for "Trust in Me (The Python's Song)" in The Jungle Book, using completely different lyrics.
A song about Admiral Boom was written for the film. Although the song does not appear in the film, the music can be heard in the score.
All 4 of Disney's sound stages were used during production.
Although Dick Van Dyke considers this the best film he has appeared in, he nevertheless maintains to this day that he was somewhat miscast as Bert. He has suggested that either Jim Dale or Ron Moody would have played the part better.
At the time, the most expensive film produced by the Disney Studios.
Bert's jobs in the film are a one-man band, a chalk artist, a chimney sweep, and a kite salesman.
Filmed entirely on soundstages under heavy studio lighting.
For her interaction with the animatronic robin, Julie Andrews had yards of control wires hidden under her costume and running up her sleeve.
His role as Constable Jones became the last on-screen role for Arthur Treacher.
In addition to Mary Martin, Bette Davis, Angela Lansbury was also considered for Mary Poppins, while Danny Kaye, Fred Astaire and even Cary Grant were briefly considered for the role of Bert.
In her 2004 autobiography "'Tis Herself", Maureen O'Hara says she pitched the idea to Disney of making a film version of the book "Mary Poppins", which was rejected. Soon after, Walt Disney purchased the rights to the book.
In the transition from page to screen, the Banks family manages to lose a set of twins, John and Barbara.
Lyricist Robert B. Sherman had searched for nearly two weeks for a catchy phrase that could be Mary Poppins' anthem. He came across the perfect title when his seven-year-old daughter Laurie came home from school one day and announced that she had just received a polio vaccine. Thinking that the vaccine had been administered as a shot, Sherman asked, "Did it hurt?" She replied, "No. They just gave it to me on a cube of sugar and I swallowed it down." Sherman tried the idea on his brother the following morning, Richard M. Sherman put the phrase to music and "A Spoonful of Sugar" was born.
Many of the nannies in the large queue of applicants for the job at the start of the film were actually men in drag.
Mary Poppins and Mrs. Banks never speak to each other in the film.
Mrs. Banks's first name was originally Cynthia. It was changed to the "more British-sounding" Winifred at P.L. Travers's request.
Not only was "Feed the Birds" Walt Disney's favorite song in the film, but it is said that anytime he visited the Sherman brothers (Robert B. Sherman and Richard M. Sherman) during the rest of his life, all he would have to do was say, "Play it," and they knew he wanted to hear "Feed the Birds".