Creator Backlash: P.L. Travers called the second chapter of the first book, "The Day Out", the worst Mary Poppins story she ever wrote. However, she apparently never said how much of her hatred, if any, stemmed from Walt Disney using its concept of jumping into chalk drawings as a way to shoehorn animation into the movie.
In addition to playing Mr. Banks, David Tomlinson voices Mary Poppins's umbrella. He also voiced some of the animated characters in the chalk drawing scene.
Julie Andrews whistled for the robin and was one of the female pearlies during "Supercalifragilisticexpialidocious."
In the musical, depending on the production, the actress who plays Miss Andrew also plays either Queen Victoria or the Bird Woman.
Creator Backlash/Disowned Adaptation: P.L. Travers absolutely hated the film, due to its changing of several elements of her original stories and the inclusion of the animated sequence. So much so, that at the premiere, she approached Walt Disney before its first screening, demanding the sequence be removed. Disney refused, and later, when the film had concluded, Travers broke down crying, not because the people hated the film, but because they were giving it a standing ovation.
Development Hell: Walt Disney had first considered making a live-action adaptation of Mary Poppins as early as 1938, but P.L. Travers didn't think it could do justice for her books, mainly because Disney hadn't done any live-action films at the time.
The medicine bottle that pours different colors was a real working prop. The children were not informed of its purpose, so Karen Dotrice's shriek of delight is real.
The children were unaware that Mr. Dawes Sr. was played by Dick Van Dyke. According to Karen Dotrice (Jane), she didn't know till she saw the end credits.
Likewise, Karen Dotrice says that in the scene in which the children run away from the bank and get grabbed by a mysterious figure, they weren't told beforehand that the soot-covered figure was actually Bert, who was trying to calm them down.
Fake Brit: Dick Van Dyke. That accent. Ironically, he also plays Mr. Dawes, Sr, doing so brilliant a job that many viewers don't even realize it was him.
In an interview filmed when she was an adult, Karen Dotrice claimed that she didn't realize it was Van Dyke until his name unscrambled in the credits at the premiere!
Dick van Dyke's Cockney accent is a contender for second most notorious film example of all time. If you're wondering who owns the title for most notorious, see here. Dick defended himself on NPR's Wait, Wait, Don't Tell Me by explaining that his accent coach was J. Pat O'Malley, who didn't speak Cockney any better than he did.
According to some Brits, it's actually a pretty decent version of the music hall Cockney accent, which only existed on stage.
Though J. Pat O'Malley was English, he was from Burnley, Oop North and nowhere near London. To hear his take on Cockney listen to Jasper in the original 101 Dalmatians, for whom he provided the voice.
In addition, Constable Jones, the police officer who brings Jane and Michael home, and is summoned to investigate the disappearance of Mr. Banks is none other than both Jeeves and Merv Griffin's sidekick/announcer, Arthur Treacher.
The old crone that the children run into while fleeing from the bank is Betty Lou Gerson, the voice of Cruella De Vil.
Uncle Albert is played by Ed Wynn, who appeared in numerous Disney films, most notably being the voice of the Mad Hatter in Alice in Wonderland.
In addition, the film's vocal coach, J. Pat O'Malley, also appeared in numerous Disney films; he was also in Alice in Wonderland, voicing Tweedledee and Tweedledum, and he was also Colonel Hathi in The Jungle Book.
Hermione Baddeley, who played Ellen, the Banks' parlormaid, also was the voice of Madame Adelaide Bonfamille in The Aristocats.
In addition, Thurl Ravenscroft, who voiced the hog in the barnyard scene in the animation sequence, also appeared in The Aristocats as the Russian cat.
Director Robert Stevenson spent much of his career directing live-action Disney films.
In addition, music editor Evelyn Kennedy also worked on various Disney films, live-action and animated alike.
After the film's success, Disney approached Travers for rights to film the other books, but given her absolute hatred of the movie, she unsurprisingly refused.
Walt was negotiating to have the rights to film Bedknobs and Broomsticks in case negotiations for the rights to Mary Poppins fell through.
The book had a chapter in which Mary Poppins and the children use a magic compass to visit different countries. The Sherman Brothers wrote a wide assortment of songs to use for their journey, but the chapter ultimately went unadapted.
Although Julie Andrews was marvellous in her Oscar-winning turn as the magical nanny, you can't help but wonder what might have been if an earlier choice for the role had been the last; Angela Lansbury was seriously considered before Andrews was finally cast.