During the fellatio scene, the crew walked out on the production refusing to take part. A similar incident happened during the shooting of Basket Case (1982).
On the subway, Brian sees a man carrying a big basket with a lock on it. The character is Duane Bradley with Belail inside the basket from Frank Henenlotter's previous film, Basket Case (1982).
The theatrical and original home-video releases of his film deleted the most gruesome scenes, such as the "fellatio" gag.
One of the gurgling sound effects used for Aylmer actually came from star Rick Hearst. Hearst's stomach would make gurgling sounds if the actor drank coffee on an empty stomach. When Frank Henenlotter found this out he had Hearst go into a sound booth and record the noise with a microphone placed against his stomach.