9. Jason Voorhees Is The Killer In The Original Friday The 13th
Here's a common misconception that probably only affects those people who haven't actually seen the classic horror flick Friday the 13th, but one that might well blow your mind if you've avoided this movie and have relied on your own brain power to work out the plot in your head. Because whereas Jason Voorhees is certainly the terrifying murderer in pretty much every sequel since the original, he isn't the one terrorising the kids in the first installment. Yep: if you haven't seen this movie, you'll likely be shocked to learn that it's actually Pamela Voorhees (played by Betsy Palmer), Jason's mother, who goes on a kill crazy rampage over the course of this iconic slasher. It wasn't until the sequel that her son - who survives the events of this movie - became the mask-clad face of the series. If you've seen the movie, of course, this isn't interesting at all, but for those who haven't, it might come as something of a revelation.