By his own admission, director Paul Schrader says that one day he got so stoned on set that he refused to come out of his trailer. A whole day's filming was lost.
The director liked Frankie Faison's performance as "Det. Brandt" but in editing didn't feel his voice worked, so it was dubbed by that of African American actor Albert Hall.
On Oliver's nightstand there's a copy of the book "Mishima: A Biography." Director Paul Schrader would a few years later go on to direct qv_ Mishima: A Life in Four Chapters (1985)_ based in part on that biography.