10 Movies That Accidentally Set Up Sequels

Much like Halloween, it's basically impossible to consider 1980's Friday the 13th outside the context of the dozen-movie franchise it spawned.

The original film ends with the twist revelation that the killer terrorising Camp Crystal Lake wasn't Jason Voorhees himself but his vengeful mother, Pamela (Betsy Palmer), who is then decapitated by Final Girl Alice (Adrienne King).

In the final scene, Alice has a nightmare where she's attacked by a thoroughly decomposed Jason, before waking up in the hospital safe and sound.

And though the closing moments suggest that Jason is still hiding out at Camp Crystal Lake, screenwriter Victor Miller had no plans at all for the film to generate a series with Jason as the killer. In an FAQ on his personal website, he said:

"To be honest, I have not seen any of the sequels, but I have a major problem with all of them because they made Jason the villain. I still believe that the best part of my screenplay was the fact that a mother figure was the serial killer - working from a horribly twisted desire to avenge the senseless death of her son, Jason. Jason was dead from the very beginning. He was a victim, not a villain. But I took motherhood and turned it on its head and I think that was great fun. Mrs. Voorhees was the mother I'd always wanted - a mother who would have killed for her kids."

But of course, Friday the 13th was a colossal box office smash beyond anyone's expectations, and so a franchise was born, with Jason taking up the murderous mantle from his mother from that point on.