Matthew Garber's final film role. He died of hemorrhagic necrotising pancreatitis on June 13, 1977, at the age of 21, in Hampstead, London, England.
Ed Wynn's final film role. He died of throat cancer almost a year before the film was released, on June 19, 1966 in Beverly Hills, California.
Many of the same special effects used for this movie were also used in Disney's earlier film Darby O'Gill and the Little People.
The title song, a.k.a. "The Gnome-Mobile Song", was written by Richard M. Sherman and Robert B. Sherman. They were also the songwriters of the songs in Mary Poppins, which also featured Ed Wynn, Karen Dotrice and Matthew Garber.
Throughout his career, Walter Brennan approached roles in one of two ways: with teeth or without, as he had false teeth. In The Gnome-Mobile, he had it both ways: teeth in for D.J. Mulrooney, and teeth out for Knobby the gnome.