According to Alfred Marks, he, Peter Sellers and Spike Milligan all read for the part of the Great Mendoza.
Wally Stott provided a score for the film, and shortly afterwards went on to write the theme tune for "Hancock's Half Hour". The Hancock theme begins with a memorable motif of six bars. Throughout the film, you can hear the very same motif as incidental music.
William Hartnell (Detective Inspector Martin) and Jon Pertwee (Charley Sterling) both later played the Doctor in Doctor Who (1963): Hartnell played the First Doctor from 1963 to 1966 while Pertwee played the Third Doctor from 1970 to 1974.
Lionel Jeffries' first credited film appearance and one of the very few films in which he appears clean-shaven.