Alec Guinness performed the stunt of climbing down the side of the mansion. He was convinced by a technician that the piano wire holding him up would not break, since only piano wire with kinks in it would be prone to breaking. As he got to about four feet from the ground, the wire did in fact break.
The strange noises made by the laboratory apparatus were created by uncredited sound editor Mary Habberfield, and produced for the soundtrack with a tuba and a bassoon.
The fictional synthetic fiber in the film is made from a "long-chain molecule...of infinite length". Nothing like that existed in 1951, but similar synthetic polymers are now a reality. In 1968 the unusual properties of "Ultra-high-molecular-weight polyethylene", or UHMWPE, were first discovered. These are extremely long-chain molecules comprised of millions of individual atoms. UHMWPE wasn't commercialized until the 1990s and it's available now under the brand names Dyneema and Spectra. Variations of these molecules are used in protective armor, cut-resistant gloves, tear-resistant hosiery, bow strings, automotive winching rope, fishing line, high-performance sails, and in climbing cord and webbing. While modern materials don't have all the properties of the fictional fiber depicted in this film it has become much closer to reality.
The sounds of Stratton's experiment (described on the record label as "guggle glub guggle") were set to music by Jack Parnell and released on Parlophone R 3435 as "The White Suit Samba" with words by T.E.B. Clarke.
The film was based loosely on a play by Roger MacDougall which had never been produced on stage at the time the film was made. MacDougall was very dissatisfied with it and showed it to his cousin, the film director Alexander Mackendrick; the latter suggested that it might work better as a film, also recommending a great many changes to the story and leading characters. The two men collaborated on the film, also bringing in a third writer who also made several changes. After the film's considerable success, MacDougall's original was staged (not in London), but without success.