Julie Andrews initially turned down the role of Miss Eglantine Price. She eventually reconsidered, believing she owed her movie career to Walt Disney Studios and wanted to work there again. When she told the studio she'd changed her mind, Dame Angela Lansbury had already been cast.
Angela Lansbury hated what she called "by the numbers" acting in this movie. Due to the heavy special effects, the entire movie had to be storyboarded in advance, shot for shot. Every moment was pre-determined, and Lansbury wasn't free to explore her character naturally.
This movie was developed at the same time as Mary Poppins (1964). Walt Disney started with this movie, decided it was too complicated technically, and switched over to Mary Poppins. They switched back and forth between movies a few times. They intended to drop this movie permanently at one point, but The Sherman Brothers, who did the music for both projects, insisted that Disney finish it after they were done with Mary Poppins.
Several of the dolls Carrie admires in the nursery of Professor Emelius Browne's house were modelled after the international puppets in the Small World ride at Disneyland.
This is the last feature film for which longtime Disney studio songwriters Richard M. Sherman and Robert B. Sherman wrote songs until The Tigger Movie (2000). They briefly returned in the early 1980s to write songs for EPCOT Center. This might have been the last DISNEY movie they wrote songs for, but it wasn't the last MOVIE they wrote songs for. For example, they also wrote the score for Tom Sawyer (1973), for Chitty Chitty Bang Bang, and for a live action retelling of the Cinderella story, The Slipper And The Rose.