Bakshi's car is a Morgan Sports Model, built from 1932-1939. Note that is has right-hand drive like all UK vehicles.
During the scene in which Peter Sellers wrecks the upstairs bathroom, the band downstairs can be heard playing "It Had Better Be Tonight," which was originally written and used both as a vocal and as an instrumental score in the first "Pink Panther" film.
Production designer Fernando Carrere reused the fireplace he had designed for The Pink Panther in this film.
The films interiors were shot on a set, at the MGM lot.
The unusual red sculpture on the wall behind the dining room table is a Mexican "árbol de la vida" (tree of life). They are still manufactured today.
This film was improvised from a 56-page outline. Each scene was shot in sequence, and built upon the previous scene. To aid in this experiment, the film's producers had a video-camera tube attached to the Panavision camera and connected to an Ampex studio videotape machine, allowing the actors and crew to review what they had just filmed.