This was Doris Day's last appearance in a full-on musical - and one of the last of the lavishly-budgeted MGM musicals as well. Despite Day being ranked the #1 box office star at the time of its release, it was widely considered a box office failure.
The dubbing of Stephen Boyd's vocals is a lingering mystery in the annals of movie musicals. Various sources have credited the robust baritone to a studio singer named James Joyce, but Joyce's name is documented nowhere else in terms of film history, and his distinctive voice has been heard in no films before or since. Additionally, contract singers were extinct by 1962, so the mystery as to who dubbed Boyd's vocals remains a Holy Grail to film historians. Further, Columbia Records' original sound track album erroneously credited Boyd for the vocal performance, which only intensifies the mystery.
This movie was based on Billy Rose's 1935 Hippodrome extravaganza and one of Rose's stipulations in negotiating the screen rights was that his name be featured in the title.
Jumbo marked the final musical arrangements and orchestrations from legendary composer Conrad Salinger, who passed away during the production.
Historical records show that many of the character names and songs of Billy Rose's "Jumbo" in the 1935 stage production were entirely different. Jimmy Durante appeared in the original New York stage production, but not as the owner of the circus. He is listed as "Claudius B. Bowers", a character name not in the film.