Betsy Palmer said that if it were not for the fact that she was in desperate need of a new car, she would never have taken the part of Pamela Voorhees. In fact, after she read the script she called the film "a piece of shit".
One critic was so angry at Betsy Palmer's role in the movie (which had angered many of her fans), that he published her address in his magazine, and encouraged people to write her and protest her. He published the wrong address.
The filmmakers never intended to make this the launching pad for the series that followed. According to Victor Miller, Jason was only meant as a plot device and not intended to continue on his mother's grisly work.
Composer Harry Manfredini has said that contrary to popular belief, the famous "Chi, chi, chi; ha, ha, ha" in the film's score is actually "Ki, k,i ki; ma, ma, ma". It is meant to resemble Jason's voice saying "Kill, kill, kill; mom, mom, mom" in Mrs. Voorhees's mind. It was inspired by the scene in which Pamela Voorhees seems to be possessed by Jason and chants, "Get her, mommy! Kill her!" Manfredini created the effect by speaking the syllables "ki" and "ma" into a microphone running through a delay effect.
While most of the cast and crew stayed at local hotels during the filming, some of the loyal cast and crew members, including Tom Savini, and Taso N. Stavrakis, stayed at the actual camp site. They had Savini's Betamax VCR and only a couple of movies (Barbarella and Marathon Man) on videotape to keep themselves entertained, so each night they would watch one of these movies. To this day, Savini says he can recite those movies by heart.
Willie Adams was a crew member for the film. Although he spent most his time working behind the camera, he played the male counsellor in the 1958 scene, and holds the unique distinction of being the first murder victim in the Friday the 13th film series.
In 1987, Warner Bros. released the film on home video in the UK. Shortly after, they realized they made a typo on the back cover in the film's credits ("Harry Crosy" instead of "Harry Crosby"). They quickly rectified this mistake and released a slightly altered cover the next year.
At one point, Mrs. Voorhess slaps Alice around a few times. Having worked onstage for years, Betsy Palmer was used to really striking her co-stars with a cupped hand along the jawline to achieve the scene. Sean S. Cunningham had to tell her about faking the blows and cheating with camera angles.
There is a township named Voorhees, New Jersey, which is about eight miles away from Haddonfield, New Jersey, which was inspiration for the fictional town where the movie Halloween took place. The documentary _Halloween: 25 Years of Terror (2006)_ shows a picture of a road sign that lists Voorhees right under Haddonfield.
The trivia items below may give away important plot points.
During the first few weekends of the film's release, makeup/effects artist Tom Savini would go into theaters for the last five minutes of the show to see the audience react to Jason emerging from the lake and grabbing Alice.
In the scene where Bill is found impaled to a door with arrows, his eye twitches continually because the eye effect that Tom Savini applied was actually burning his eye and causing him excruciating pain.
There is rumored to be a deleted scene featuring the murder of Claudette. The crew of the film dismissed this, including Tom Savini, who said he never even worked on the opening scene. There is, however, a still of Claudette with a machete in her throat, although that may have been shot purely for promotional material.
Kevin Bacon's character, lying in bed with his throat impaled by an arrow, has the blood in his neck making little bubbles. Originally, it was just meant to seep out, but the arrangement of the tube with blood didn't work, and Tom Savini ended up blowing into the tube to make it flow, causing an unintended (but ultimately used) bubbling effect.
Top-billed Betsy Palmer does not actually appear on screen for more than 13 minutes. Ironically enough, a stand-in male actor was used for the first 70 minutes of the film in which she is never supposed to be recognized.