These facts came via the documentary Supercalifragilisticexpialidocious: The Making of Mary Poppins, unless otherwise stated.
1. Walt Disney first began pursuing the rights to the book in 1938, but was rejected by the book's author, P.L. Travers.
2. Over the years, Walt Disney continued to make offers for the book's rights. In 1959, he and Travers finally met in person in London. She agreed to option the book to him.
3. Iconic Walt Disney Studios' songwriters — and brothers – Robert Sherman and Richard Sherman, worked on the music for the film for 2.5 years, unaware that the studio did not have the full rights to the book.
4. Walt Disney originally considered Angela Lansbury, Mary Martin, and Bette Davis for the role of Mary Poppins.
5. Robert Sherman was the first to consider Julie Andrews for the title role after he saw her and Richard Burton perform a song from Camelot on The Ed Sullivan Show.
At the time Andrews and Burton were both appearing in the show on Broadway.
6. Julie Andrews agreed to make the film after she was rejected for the role of Eliza Doolittle in the film version of My Fair Lady.
Andrews' had originated the role of Doolittle — to much critical acclaim — playing her on both Broadway and London's West End.
Julie Andrews was considered a shoo-in for the film, but then-Warner Bros. President Jack Warner decided she was too much of an unknown to carry the film and cast Audrey Hepburn instead.
7. The film marked Julie Andrews' big-screen debut.
8. David Tomlinson, who played Mr. Banks in the film, also provided the voice of Mary Poppins’ parrot head umbrella.
9. At the beginning of the film, some of the nannies waiting in line to apply for the nanny position were actually stuntmen in drag.
10. Dick Van Dyke’s notorious Cockney accent was partially to blame on his Irish vocal coach Pat O'Malley, who, according to him, “didn't do an accent any better than I did.”
Source: NPR
11. This was the second of three Disney films that Matthew Garber (Michael Banks) and Karen Dotrice (Jane Banks) co-starred in.
12. The "Step in Time" dance sequence was originally slated to be nine minutes long, but the director tried to cut it down to two after fearing it was too long. When Walt Disney found out, he actually decided to add more elements to the sequence, extending it to 14 minutes.
The cast rehearsed the "Step in Time" dance sequence for six weeks.
13. Prior to this movie, Dick Van Dyke had never received any type of dance training.
14. Julie Andrews' hair was a wig.
15. According to Richard Sherman, "Feed the Birds" became Walt Disney's favorite song and Sherman would often play it for him on the piano.
View this video on YouTube
16. Even though Dick Van Dyke was already cast at Bert, he really wanted to play the role of the villainous old bank president Mr. Dawes. He persuaded Walt Disney by screen-testing for the role and agreeing to make a donation to Cal Arts.
At the end of the the film, his credit for the role first appears as "Navckid Keyd," which is an anagram for Dick Van Dyke.
17. According to Richard Sherman, it took him and his brother two weeks to come up with the word "supercalifragilisticexpialidocious," and that the word was based on a double-talk word from their childhood.
18. By the time of the film's star-studded premiere, relations between P.L. Travers and Walt Disney Studios were so frosty that she wasn't even invited. She had to ask Disney for permission to attend.
19. The film was not only one of the highest-grossing films of 1964, but also, at the time, Walt Disney Studios' highest-grossing film ever.
20. After the film became a huge hit, Walt Disney Studios made plans for a sequel, but P.L. Travers turned them down.
21. At the 22nd Golden Globe Awards, Julie Andrews, who was nominated for Best Actress in a Musical or Comedy, got a bit of revenge on Jack Warner...
...by beating out his casting choice Audrey Hepburn, who was also nominated in the same category for My Fair Lady, for the award...
...and she even took a small jab at Warner by thanking him during her acceptance speech, for not casting her as Eliza Doolittle.
Andrews also took home the Academy Award for Best Actress. Hepburn wasn't even nominated.
