Peter Sellers made this film in part as a means of emulating his hero, Alec Guinness, by playing multiple roles in one movie.
Jack Arnold did not ask the studio's permission to make fun of the Columbia logo, convinced they would say no. At the film's opening, "Miss Columbia" discovers a mouse under her skirts and runs off screaming. At the end she returns to her pedestal. Studio executives first heard of the joke when they attended the New York previews, where it got a huge laugh. After that, there was no thought of cutting it, though it is absent from some television prints.
The Marseilles and New York harbor sequences were filmed in Southampton, UK. The presence of the Queen Elizabeth ocean liner there was a lucky coincidence.
Jack Arnold soon learned that Peter Sellers did his best work on the first take and was usually useless by take three. The actor, schooled in improvisation, couldn't keep the lines fresh if he had to say them over and over.
The New York invasion sequence was filmed in Manhattan on a Sunday morning, accounting for the city's empty streets.
The scenes in the ports of Marseilles and New York were both shot in Southampton. By luck, Queen Elizabeth was just landing there at the time, so Jack Arnold had extras on the Fenwick tugboat get as close to the luxury liner as possible and fire arrows at her. Later he added a scene with Stuart Sanders as the Queen Elizabeth's captain reacting to the attack.
The Grand Duchess' car is a 1913 Sunbeam 12/16.
Peter Sellers modelled the Grand Duchess on his grandmother. He also used shtick he had developed for the radio series Ray's a Laugh, in which one of the characters he played, was an eccentric old woman named Crystal Jollibottom.
Used to working with Otto Preminger, who would scream at her even before the first take to get the performance he wanted, Jean Seberg had trouble adapting to Jack Arnold's gentler directing style. It often took as many as 20 takes for her to get through a scene.
The palace band includes a double flageolet, a 19th century wind instrument.
Jean Seberg only had one line in the first scene shot, which she shared with Peter Sellers and Leo McKern. For the first several takes, she stepped forward for her line, then back when she was finished. When Arnold pointed this out to her, she said she didn't even know she was doing it. By the time she got her movements under control, she couldn't remember the line. After 25 takes, Arnold postponed the scene until a few days later.
While filming, Peter Sellers was acting on stage in the comedy Brouhaha, which also dealt with a mythical kingdom whose ruler develops an outlandish plot to secure U.S. aid. Five days a week, he had to be at the studio at 6:30 a.m. for makeup and wardrobe, then get himself to the theatre by 7 p.m. During location shooting, a driver picked him up at the theatre after the performance and he slept in the car on the way to the film shoot.
The invasion of Manhattan was shot in a section of London that had been completely rebuilt after being bombed heavily during World War II. The glass and concrete high rises provided a perfect stand-in for New York. Jack Arnold also filmed background shots on the streets of New York early one Sunday morning, when traffic was at a minimum.
Among the musical quotations used by Edwin Astley in the film were excerpts from Felix Mendelssohn's "Hebrides Overture", "Rule Britannia", "A Life on the Ocean Waves", "Frankie and Johnnie", a number of American marches, including a number of passages from "Our Director" and Astley's own score for The Adventures of Robin Hood (1955).
Although Jack Arnold and Walter Shenson thought the dailies were hilarious, Carl Foreman and Columbia's European head didn't get it. Their lack of response was so discouraging, Arnold stopped going to the daily screenings.
The castle of Grand Fenwick was a façade built on the back lot of England's Shepperton Studios. Jack Arnold also used the surrounding countryside as the forests of Fenwick.
Peter Sellers modelled The Prime Minister on Alec Guinness' interpretation of Benjamin Disraeli in The Mudlark (1950).
The AFI online Catalog reports the showing of this film to diplomats in Geneva, Switzerland on 23 May 1959. There is no mention of the circumstances of the showing.
Columbia previewed the film at two different New York theatres, the Trans-Lux, which was an art house, and Loew's 84th Street, which showed more popular entertainment. Both audiences roared with laughter. As a result, Foreman recalled the prints so the titles could be changed from "High Road presents" to "Carl Foreman presents."
One scene has diplomats playing a board game called Diplomacy, although the game more resembles Monopoly rather than the game Diplomacy.
As there is no actual mouse in the film, title designer Maurice Binder added one in a classic opening joke with the Columbia Pictures logo and a return of the mouse in the last scene.
The British and American prints of the film vary in their opening narration, using British and American voices respectively.
The tiny ship that transports the Grand Duchy's soldiers is the Paladin.
Duchess Gloriana XII has a personalised number plate on her car: G XII.
Grand Fenwick is ruled by Duchess Gloriana XII, said to be still in mourning for her consort "Count Leopold of Bosnia Herzegovina". The country of Bosnia and Herzegovina was at that time absorbed within the Republic of Yugoslavia, then under Communist rule. It is likely that many viewers thought "Bosnia Herzegovina" was as fictitious as Grand Fenwick. Bosnia and Herzegovina only became a sovereign nation again in 1992, after the Balkans conflict had resulted in the break-up of Yugoslavia.
Opening credits: All characters and events in this film are fictitious. Any similarity to actual events or persons, living or dead, is purely coincidental.