Friday the 13th Part 5 tries to make it a mystery whether Jason has returned or not, but a tiny detail gives away that the killer is a copycat. In Friday the 13th Part 4: The Final Chapter, Jason Voorhees was quite definitively killed off, being hacked up with a machete by a young Tommy Jarvis. Jason had never been depicted as a supernatural being up to that point, so when he died, it seemed real. The problem was, The Final Chapter made a ton of money, making Paramount reconsider its decision to conclude the franchise.
Thus, the following year saw Friday the 13th Part 5: A New Beginning hit theaters. However, it wouldn't make any sense for Jason to just be alive again with no explanation, so they opted to write around that problem by introducing a killer that attempted to emulate Jason. Of course, producers knew advertising the fact that Jason wouldn't be in the movie would keep fans away, so instead they tried to turn it into a mystery. Was Jason back from the dead? Had Tommy gone insane and taken up his mantle? Sadly, the answer was much stupider.
Friday the 13th Part 5's new killer was Roy Burns, a paramedic seen briefly early on in the film, taking revenge for the death of a son that the audience didn't even know was his. It felt like a lame cheat to fans, and well, it kinda was. However, those paying attention could spot a clue right away that the killer wasn't actually Jason.
Friday the 13th Part 5: The Tiny Detail That Gives Away the Twist
The clue to Friday the 13th Part 5's killer not really being Jason Voorhees is in some ways so obvious that it really should've been noticed immediately. Then again, in 1985, the internet didn't exist to allow everyone to obsess over their favorite movies, making it more likely audiences wouldn't be looking that hard. Anyway, said clue involves Jason's trademark hockey mask. In Friday the 13th Part 3, Part 4, and generally, Jason's mask has three red triangles on it, one above his eyes pointing down and two on the sides of his face pointing up.
When Roy Burns is pretending to be Jason in Friday the 13th Part 5, his mask has only two blue triangles on the sides, both pointing down. This mask design was never used before, and never used again after A New Beginning, and is a dead giveaway to any dedicated Jason fan that the killer isn't Mr. Voorhees. Interestingly, the filmmakers seem to have inserted this clue on purpose, as in scenes where Tommy Jarvis dreams of or hallucinates Jason, he has the old three red triangles mask look. Friday the 13th movies are rarely lauded for their continuity, but that's actually a pretty cool touch.