In the police station on "no crime" night, one of the cops can be seen reading a comic book based on the U.S. television show Car 54, Where Are You? (1961). Joe E. Ross and Fred Gwynne can be seen on the cover.
The white Ferrari in which Peter Sellers pulled up at the fairground was his own. It's a Ferrari 250GTE, registration 5 XPC, one of several Ferraris owned by him. As at May 2017, it is now red and is in the U.S.
Scandinavian actor Tutte Lemkow played the German safecracker, "Siggy Schmultz". He appeared in many British movies and usually voiced himself (though many of his roles were non-speaking). Here, however, he was dubbed by Peter Sellers, which means that in Lemkow's scenes, Sellers can actually be heard conducting conversations with himself.
Many of the rides seen in the amusement park sequence can be seen in the opening credits of the Hammer TV series "Journey to the Unknown."
Bluey (Ed Devereaux), one of the Australian gang, was a main character in the television series about a resourceful kangaroo, Skippy (1968).
After Pearly Gates (Peter Sellers) has shown his gang a movie he shot showing the jewelry shop manager opening his safe and thus providing them with the combination, one of the gang asks, "What's on next week?" Sellers replies "A few educational films and training films. Starting off with Rififi (1955).. "the French film"...The Day They Robbed the Bank of England (1960)...followed by The League of Gentlemen (1960)...After that we're having a discussion of what we've learned from all three films." Each of these titles is an actual movie released between 1955 and 1960 depicting burglaries.
The cast includes Lionel Jeffries, who directed The Railway Children (1970), and Bernard Cribbins, who played a major character in that movie.
Two of the writers, Galton and Simpson, created BBC television's Steptoe and Son (1962) (Sanford and Son (1972) in the U.S. remake) and also wrote BBC television's Hancock's Half Hour (1956).