Supermodel Twiggy and her manager/boyfriend Justin de Villeneuve were given brief cameo roles during the court scene, and appear as a male courtier and a tall silver-wigged gentleman respectively. However once the nuns started stripping Twiggy walked off the set and the pair only filmed one shot.
A major sequence in which the nuns tear down and ravish a life-sized icon of Christ in an orgiastic frenzy was cut from the film and subsequently vanished. Film critic Mark Kermode discovered the footage many years later. Director Russell was keen to reinstate the scene but found that Warner Brothers were not interested in doing a director's cut. The footage can be seen in a documentary Kermode made about Russell and was subsequently included in an uncut DVD release.
Early in the movie when Urbain Grandier (Oliver Reed) is seen grooming his hair. It is a close-up of him supposedly looking at a mirror in the upper left hand corner of the screen, behind the viewer. Obviously there is no mirror as he consistently misses combing the more egregiously messed up parts of his hair and instead repeatedly combs the portions that are already groomed. In fact when he is done, his hair is still messed up.
Barre: [blessing the torture instruments with holy water]
We humbly beg of thee almighty God, in thy goodness, bless these instuments thou has created and given to us for our sacred use...