Like many other classic horror movies from the 70s and 80s, Friday the 13th had its share of production blunders, including being unable to cast the role of Pamela Voorhees.
Because the role was so vital to the film, given that Pamela Voorhees was Friday the 13th's original killer, it's surprising that director Sean S. Cunningham took so long to cast the role. Eventually, Cunningham found Betsy Palmer, who stepped up to the role and became known for it, despite her initial thoughts that nobody would go out and see the film. Though Palmer had an acting career before taking on the role, Pamela Voorhees became her legacy and she learned to embrace it over time, rather than hide from it or try to trash the production as the franchise's popularity soared to incredible heights.
Sean S. Cunningham belongs on a long list of horror directors who have had major issues during production of films that would eventually make their career, as not having a Pamela Voorhees would have likely ruined Friday the 13th.
Betsy Palmer Wasn't Cunningham's First Choice
Originally, Cunningham had his eyes on a different actress for Jason's mom: Shelley Winters. His initial thought was that having a known actress in the role would draw in an audience and what he couldn't grab with concept alone, he could grab with a big name on the marquee. Ambitious as ever, Cunningham courted Winters, who won the Academy Award for Best Supporting Actress twice, once for her work in The Diary of Anne Frank (1959) and A Patch of Blue (1965). She was a skilled actress, known for both stage and screen, and had developed a career as a "blonde bombshell" figure in Hollywood. Winters shot him down outright. Another Academy award-winner, Estelle Parsons (Bonnie and Clyde, 1967), negotiated for the role of Mrs. Voorhees and showed genuine interest, but backed out at the last minute. Even so, Cunningham persisted and auditioned other actresses, but ultimately it was Betsy Palmer who grabbed the role, and not because she was in love with the part. Palmer has said, quite candidly, that if her car hadn't broken down on a trip home to Connecticut, leaving her in need of money for a new one, she likely would have turned down the role.
Friday the 13th Started Filming Without Mama Voorhees
Though it seems more like artistic license to leave the killer vague throughout the course of Friday the 13th, it was born out of necessity as filming had to start without someone in the role. Many scenes were shot before Palmer started shooting, while contracts were still being negotiated, so other various crew members had to stand in and assist. Cunningham did his best to limit the shots and make it so there wouldn't be an obvious error when the killer was confirmed to be a middle-aged woman, but some scenes show hands that aren't particularly feminine, and weren't re-shot after Palmer was cast. One particular scene, where Annie has her throat slit, the hands of special effects assistant Taso Stavrakis can be seen holding the knife. Most of the early murder scenes were filmed in this capacity with limited parts of the killer being shown for a very good reason.
When Palmer did step up to the role, she did so wholeheartedly, giving an incredible performance and bringing a level of character to Mrs. Voorhees that seems so uniquely her. As a Method actor, Palmer developed her own backstory for Jason and Pamela; she devised that the reason why Mrs. Voorhees was so angry at the promiscuous teens was partially because she was a young, unwed mother who had latent psychotic rage regarding sexuality, despite how maternal she was with her son, Jason. Palmer passed away in 2015.