Gene Reynolds, who plays Frankie, would go on to a successful career as a TV producer and director, most notably of M*A*S*H.
In the movie, the newspaper account lists Jascha Heifetz's stolen Violin as a Stradivarius. Heifetz actually used a Guarnarius in the picture and favored that violin in real life, but the producers felt that the name of Stradivarius would be more recognizable.
One of the few films in which conductor Alfred Newman actually makes an on-screen appearance.
The tall violinist in scenes with the California Junior Symphony Orchestra standing at the far end was Raymond D. Bowman, a child prodigy from Long Beach, who was 21 at the time. In 2 more years, he would be in the Army and survive the Japanese attack on Pearl Harbor on 7 December 1941. In the 1950s, he was one of the first members of the "Pearl Harbor Survivors Association" and was a classical music critic for many years for the South Bay Daily Breeze in Redondo Beach.
Though Archie Mayo received sole on-screen credit as director, the scenes showing Jascha Heifetz performing were actually directed by William Wyler. Because of Heifetz' schedule, Sam Goldwyn had to complete those scenes before he had assigned a director to film the rest of the movie.