Peter Sellers had such a weak heart that he was advised not to make this movie at all. He ignored that advice and did the movie anyway. Chillingly prophetic was part of the story-line where Dr. Fu Manchu keeps his heart beating by intermittently giving himself electric shocks. This movie was Sellers' final movie. It debuted about two weeks after Sellers' death in London on 24 July 1980.
Final movie of Peter Sellers. This movie was actually the last movie in which Sellers appeared while he was alive, as Trail of the Pink Panther (1982) was released a couple of years later, which starred Sellers posthumously, it being comprised of outtakes and unused footage from the "Pink Panther" film franchise. If Sellers had lived, his likely next movie would have been "Romance of the Pink Panther", as that movie had been in development while this movie was being made.
According to "Movie News Magazine" (Australia; Vol 16, No 4), "Midway through shooting, Sellers collapsed with a mild heart attack and had to spend several weeks recuperating. When he returned to the set, he apparently disliked what had been shot in his absence, and filmed some additional scenes which he directed himself."
Peter Sellers directed most of this movie after dismissing the original director, Piers Haggard, early in the production. However, he did not alter Haggard's screen credit, and kept his own name out.
Burt Kwouk: As Fu Manchu's Servant. Kwouk worked with Peter Sellers on four Pink Panther movies. Upon seeing him in this movie, Seller's character says, "Your face is familiar." This can be interpreted as a reference to them having appeared in those four movies, as well as a reference to Kwouk's uncredited appearances in two "Fu Manchu" movies, which starred Sir Christopher Lee.