The Adventure of Sherlock Holmes' Smarter Brother is a 1975 British/American comedy film with Gene Wilder, Madeline Kahn, Marty Feldman, Dom DeLuise, Roy Kinnear and Leo McKern. The film was Wilder's directorial debut.
The hero is Sigerson Holmes (Wilder), the younger and "smarter" brother of Sherlock Sheer-Luck Holmes. Jealous of his more famous brother, Sigerson teams up with a Scotland Yard records clerk (Feldman) and a would-be opera singer (Kahn) to solve a case that Sherlock is unable to attend to, putting him up against both Moritarty (McKern) and a blackmailer (DeLuise).
Wilder was having lunch with producer Roth when it was suggested that Wilder spoof Sherlock Holmes. ...I said I had - every other week for a year. But I couldn't see making fun of such a well-loved character in a 140 minute movie. Roth approached Wilder again a week later and inquired if Wilder had given anymore thought to the idea of a Sherlock Holmes film. Wilder replied "No, but I have given a great deal of thought to Sherlock's insanely jealous brother Sigi." Wilder's screenplay belies a deep knowledge of Conan Doyle's characters as Marty Feldman's character, Sgt. Orville Stanley Sacker, shares a similar name with that originally applied to John Watson, Ormond Sacker.
The film's title and premise are a joke referring to the character of Mycroft Homes, Sherlock Holmes' older brother, who was by both of their estimates a good deal smarter than Sherlock. He was, however, too lazy to become a detective, and did indispensable work for the British government. Mycroft was described by Sherlock in conversation with Watson: One has to be discreet when one talks of high matters of state. You are right in thinking that he is under the British government. You would also be right in a sense if you said that occasionally he is the British government.
[...] Mycroft draws four hundred and fifty pounds a year, remains a subordinate, has no ambitions of any kind, will receive neither honour nor title, but remains the most indispensable man in the country.