Most of Catherine Schell's (Lady Litton's) laughter is genuine. Peter Sellers (Inspector Jacques Clouseau) made her laugh so hard once the camera was rolling, she had a real problem keeping a straight face in many of her scenes with him. This resulted in writer, producer, and director Blake Edwards giving up on trying to get her to react like she was supposed to in the script.
Douglas Fairbanks, Jr. was offered the role of Sir Charles after David Niven proved to be unavailable. After some consideration, he turned it down, paving the way for Christopher Plummer.
Dame Julie Andrews filmed a cameo role as a maid removing the unconscious Inspector Jacques Clouseau (Peter Sellers) from Lady Claudine Litton's (Catherine Schell's) room, but her part was edited out.
Unlike the other movies in the original Pink Panther film franchise, United Artists was not directly involved in the making of this movie. Because the careers of writer, producer, and director Blake Edwards and Peter Sellers were declining, United Artists had no desire to finance another Panther movie. Edwards took his script of this movie to British producer Sir Lew Grade, who subsequently bought the rights. Grade financed this movie himself, while giving United Artists worldwide distribution rights, ownership in the copyright, and a stake in the profits (as they owned the characters) in order to make the movie. Distribution rights in later years reverted back to Grade's company, ITC. This is the reason why, until recently, this movie had not been featured in compilation DVD box sets along with the other Panther movies. United Artists (via MGM) has since reacquired domestic rights to this movie and it has now been issued in a Blu-ray box set of all of Sellers' "Pink Panther" movies, while international rights are now with Universal Pictures.
The "Swine Bird" Parrot in the hotel room scene is the same blue-and-gold macaw that appeared in two of the Bond movies, For Your Eyes Only (1981) and The Living Daylights (1987).