Because producer Dick Randall was simultaneously making kung-fu films in Rome, a cameo for a Bruce Lee imitator, Bruce Le, was written into this film, even though this scene makes no sense in the context of the rest of the film.
In the only trailer released, one of the final shots shows the chainsaw killer approaching the camera. As this happens, the same scream from Janet Leigh, the scene in Alfred Hitchcock's Psycho (1960) when she gets killed in the shower scene, is used.
The trivia items below may give away important plot points.
Before the fifth victim gets killed, she's so terrified that she visibly urinates her sweatpants; this happened for real on set from a real chainsaw being wielded a few centimeters away from the actress. Juan, liked the reaction that the girl expressed and left the accident in the final film.
Originally there was supposed to be a love scene between Mary and Kendall according to the director, but Linda Day declined; so the scene with the two at the apartment, Kendall asks to come in, but Mary turns down his offer.