Somewhat overweight for much of his life up to this point and possessing a hang-dog face, Peter Sellers was obsessed with becoming a handsome leading man. Although he easily outperformed Robert Wagner in this picture, he envied the American actor's good looks. To get himself in better shape, he subjected himself to a gruelling weight-loss regimen that included the excessive use of diet pills, possibly a contributing factor to the heart attack he suffered before the film's release. Some biographers also claim he had his teeth straightened and capped.
An animated Pink Panther was created for the opening credits because writer and director Blake Edwards felt that the credits would benefit from some kind of cartoon character. David H. DePatie and Friz Freleng decided to personify the film's eponymous jewel, and the Pink Panther character was chosen by Edwards from over a hundred alternative panther sketches. The Pink Panther introduced in the opening credits became a popular film and television character in his own right, beginning with the cartoon short The Pink Phink (1964) the following year.
Blake Edwards employed multiple cameras to catch the improvisations he encouraged Peter Sellers to do.
Blake Edwards and Peter Sellers enjoyed working together to develop Clouseau down to every move and nuance of voice and expression. "For years I'd been getting bits of what I wanted into films, as writer or director . . . but I had never had an area in which to exploit my ideas to the full," Edwards said. "Then along came Peter, a walking storehouse of madness, a ham with an almost surrealist approach to the insanity of things, and we found an immediate affinity."
Claudia Cardinale could not speak English, so Princess Dala's dialog was dubbed by 20-year-old Gale Garnett.