The opening theme tune uses, uncredited, the tune of "A Policeman's Lot Is Not A Happy One", by Arthur Sullivan. Additionally, Dave Dee, who sings it, is a former policeman.
The original script, titled "Rentasleuth", was written by John Cleese and Graham Chapman. However, the pair left the project and, having seen the finished film, asked for their names to be removed. The film therefore has an "additional material by" credit, but no main screenplay credit.