The splurge guns did not actually fire the "splurge". Director Alan Parker first tried wax balls filled with cream but these hurt when fired, so in the end the splurge guns actually fired ping pong balls, which the actors fired at nothing and what we see on-screen is clever editing between this and shots of actors being hit by handfuls of cream thrown at them by others.
The pedal-driven cars could achieve a maximum speed of around ten miles (16 kilometers) per hour. They were all custom-built by hand and each cost around the same amount of money as a regular road-going Mini at the time.
Up to six teachers were on hand during production in a special full-time school adapted to space at Pinewood Studios. The improvised educational facility had to handle various teaching grades and levels from students within a five year age span and also from two different countries. Head teacher Lyn Simonon later wrote a paper about the temp film set school.
One thousand gallons of synthetic cream were used in the film by property master John Leuenberger. The original plan was to use shaving cream but this was a ballistic failure for the splurge guns and it also smarted the eyes.
The 1929 New York street complex was the movie's main and largest set. It was built on the largest sound stage at Pinewood Studios on one meter rostrums. The massive set utilized over eighty tons of concrete which had to be poured into its foundation. Real steam was piped through its base so as to gush out of the street set's manholes. The street complex had to be a constructed set rather than a real life location as the child actors were not allowed to work at night due to regulations. As such, the set could be lit for night during daytime filming.
Florrie Dugger was at first only given a minor part - until the original actress meant to play Blousey underwent a growth spurt and became taller than Bugsy (Scott Baio), and Dugger was given the role of Blousey.
Although Scott Baio was born in Brooklyn, director Alan Parker notes that he found Scott in a Los Angeles audition. Parker added that he conducted auditions for Bugsy Malone (1976) for more than a year all over Britain, including the Lakenheath USAF (U.S. Air Force) air-base in Suffolk, England, as well as conducting auditions in Harlem in Brokklyn and Los Angeles in California auditioning altogether over 10,000 youth.
Every child actor working on the movie had to have an individual medical approval and working license. The official paperwork to allow children to work in the movie was mountainous. More than thirty-three English councils were involved as well as bureaucracy in New York and Los Angeles.
Although it performed well in England and Japan, Paramount only gave "Bugsy Malone" a limited release in US theaters, usually dumping it onto second-feature screens partnered with a late-'76 re-release of The Bad News Bears (1976).
Alan Parker said he first came up with the idea for the story while driving from London to his house in Derbyshire - to keep his kids occupied, he told them this story, then his son Alexander, asked why kids couldn't be the heroes.
The development of the splurge guns took three months work by special effects boffins at Pinewood Studios. A gunsmith was consulted by fxpert Malcolm King to resolve the very complex ballistic problem of being able to shoot a capsulated custard pie without it first splurging the firer-splurger.