Jimmy O'Dea and the other actors who played leprechauns were not given any screen credit, nor did Walt Disney allow any other material to be published about them in the marketing for the film. Disney's intention was to give the illusion he was using real leprechauns for the filming. Disney even went so far as to film the Walt Disney's Wonderful World of Color episode, "I Captured the King of the Leprechauns" (#5.26), in which he and "Darby" (Albert Sharpe) manage to corner King Brian and convince him to participate in the film along with his people.
Walt Disney had seen Albert Sharpe in a stage production of "Finian's Rainbow" in the 1940s and kept him in mind for the role of Darby. By the time he began casting this film a decade later, Sharpe had retired. Disney was able to convince him to come out of retirement.
Walt Disney started planning for this movie in the 1940s. After World War II, Disney sent several artists to Ireland for background material.
Walt Disney visited Ireland in December of 1948 and publicly announced the production of this film, then entitled simply, "The Little People". It would be another decade before the film was actually made.
Walt Disney was initially hoping to cast Barry Fitzgerald in the dual roles of Darby O'Gill and King Brian. Fitzgerald reportedly declined due to his advanced age (although his eventual replacement as Darby, Albert Sharpe, was three years his senior). Disney regretted the loss of Fitzgerald in the lead role, and blamed the film's disappointing box-office performance partly on this loss.
Albert Sharpe did not know how to play the fiddle, so two professional musicians were hired to create the illusion. One handled the bowing and the other handled the frets while Sharpe kept his hands out of the way.
A version of the song "My Pretty Irish Girl" sung by Sean Connery and Janet Munro was released as a single about the same time as the debut of the movie in 1959. Ironically, Sean Connery said the singing was the one aspect of the role he wasn't too fond of.
In the original release, there were numerous asides where the Irish characters would speak in Munster Gaelic. Darby counts off "aon, dó, trí, ceathair" before playing the Fox Chase; several times King Brian rallies the hunt with a cry of "Ar aghaidh linn! (ahead with us!)" and so on. A later version had most of these lines redubbed in English.
The death of Kieron Moore (Pony Sugrue) on July 15, 2007 leaves Sean Connery (Michael McBride) as the film's last surviving cast member.
The leprechaun effects look very high tech and complicated, but most of them were achieved very simply by placing the "normal sized" actors closer to the camera than the "tiny" ones, and lining them up on the same horizontal plane through the lens so the distance between them could not be detected.
The lighting used to make sure the actors were kept in proper perspective without seeming false used up so much electricity it apparently blew out a substation in Burbank when the lights were turned on without warning.
The movie was released one year after the copyrights expired on the stories by Herminie Templeton Kavanagh.
This was the film that brought Sean Connery to the attention of Albert R. Broccoli, who then went on to cast Connery in his most famous role as James Bond.
When Michael doesn't kiss Katie, King Brian (Jimmy O'Dea) exclaims "And him a Dublin man!" O'Dea was born and raised in Dublin.