Joan Sims and Angela Douglas had to visit the Pinewood Plastering Department in order that a plaster cast could be taken of their whole body. This was in order for the dummy scenes in the film.
Charles Hawtrey was an 11th hour casting choice
Although a vocal version of the theme sung by Boz Burrell was released as a single in the UK, many people believed the uncredited singer of the theme song was Jim Dale. However it was actually performed in the movie by Ray Pilgrim, a session singer for the Woolworths-owned Embassy label.
Due to illness Sid James had to pull out of the movie, and so Harry H. Corbett was drafted in to replace him. Despite this, his character name Sidney Bung, was kept. Sid James's characters on TV and film were very often also called Sid.
In the original script, Doctor Watt was the father of Valeria. When Kenneth Williams wanted to play the part closer to his own age, the relationship was changed to that of brother and sister.
It is likely that the character name Doctor Watt was a play on the BBC character Doctor Who, who was huge in the UK at that time. Doctor Watt actually says "Who is my uncle or was, I haven't seen him for years I don't know what happened to him". Ironically, Jon Pertwee, who plays Doctor Fettle in the movie, later went on to become the third Doctor Who a few years later.
Jewelry was bought from London for Fenella Fielding to match her now iconic red dress. Fenella Fielding's had to buy her own ring for the role, however, which cost £9.
Sergeant Bung's car is a 1904 Brushmobile. The company was based in Loughborough in Leicestershire, England and only six of these cars were made. The taxi used by Bung's wife is a 1906 Renault.
Whenever Bung is using his car the soundtrack plays a variation of "Johnny Todd", the theme to the TV series Z Cars which featured the latest car-based police of the 1960s. When Bung rides on the horse and cart the tune "Old Ned" is used, the theme to Steptoe and Son which also starred Harry H. Corbett.