Ennio Morricone's musical theme "Chi Mai" was composed for Maddalena (1971). The song was completely re-recorded in 1978 for the single "Disco '78" with heavier drums and in a different key. After hearing this version on the radio, Jean-Paul Belmondo was so impressed that he suggested it should be put into the soundtrack of his film. Ultimately, the record of this musical score was not only more successful than its initial release but came to be one of Morricone's bestselling work.
The music was used again in the 80s for a Royal Canin commercial (a dog food brand) featuring slow-motion running dogs, and this became so famous that most people now associate "Chi Mai" with the commercial. It was even spoofed in Astérix & Obélix : Mission Cléopâtre (2002).
When a national tribute for Belmondo was held right after his death in 2021 in the Hôtel des Invalides, "Chi Mai" was played.
As usual at the time, Jean-Paul Belmondo is performing his own stunts including those of the car chase on The Trocadero Plaza.
While experiencing shooting delays, Jean-Paul Belmondo asked his father Paul Belmondo to help with the authorizations needed to perform the famous car chase scene on the Trocadero Plaza.
Yet another agent with the initials JB: Joss Beaumont, James Bond, Jason Bourne, Jack Bauer, et al.
Fourth highest grossing movie of its year in France. It broke the 300,000 admissions mark in Paris; a record at the time.