Peter Sellers hated the film, feeling that his character was too close to his own actual personality. After failing to buy the film negative, so that he could re-shoot the film, he went into a period of depression about it.
The stage version of the film was entitled "Call Me Daddy". It was shown on "Armchair Theatre" on British television in 1967, starred Donald Pleasence as Hoffman and is available for viewing on Youtube.
In Hoffman's apartment, beside the bathroom door, hangs the portrait of Daniel Mendoza, a famous boxer and Peter Sellers' great-great-grandfather. This same portrait hung prominently in Inspector Clouseau's bedroom in "A Shot in the Dark" and in the cottage of Nayland Smith in "The Fiendish Plot of Dr. Fu Manchu".
Alvin Rakoff had earlier directed the original TV version of this story in 1967.
When 'Miss Smith' plays 'Chopsticks' on the piano, she only uses her right hand. Whilst it's possible to play it with one hand, the usual way is with both index fingers. Hence the name 'Chopsticks'