Director William A. Graham said in an interview years after the making of this film that Elvis Presley was the nicest man he had ever met.
When Elvis is playing the piano and Mary Tyler Moore the guitar, the tune they're playing together is "Lawdy Miss Clawdy", a song that Elvis first recorded in 1956. It is the only recorded performance of this song that features Elvis on the piano.
The first film in the West to mention autism.
Mary Tyler Moore and Edward Asner would soon become co-stars of her self-named The Mary Tyler Moore Show (1970) Show. In Change of Habit, however, they shared no scenes together.