Plot hole: When Jason is going next door to chase after Trish, he pulls Jimbo's body down from the doorway and begins walking towards Trish's cabin. He is seen walking by himself. However in the next scene, he throws Rob's body through the window. There was no time for him to go back and get the body. (01:17:15)SAZOO1975
Revealing mistake: Near the end when Jason throws the hammer at the girl, it sticks to the damaged part of the wall after it hits. But it's just against the wood with the flat top, there's nothing to hold the hammer there and it's only hit the wood on the other side of the wall. They probably used a magnet to attract and keep it there for safety reasons. (01:15:00)
Continuity mistake: In Part III, Jason's fingernails were neat and trimmed, but in Part IV (which occurs the very next day), they are long and black. (00:07:00)
Continuity mistake: As Jason breaks into Tommy's room, a purple monster mask on Tommy's wall starts to spin, then stops a few shots later, then starts spinning again in the next shot. (01:16:00)
Mrs. Jarvis: Someone left the front door open again.
Tommy: We're in the country.
Mrs. Jarvis: Well, what happens if a psycho wanders in?
Trish: He'd probably challenge him to a game of Zaxxon.
Trivia: Peter Barton was hesitant when it came time to do his death scene, as he was previously burned by a magnesium flare doing a stunt on a previous film and required multiple surgeries afterwards. Sensing Peter's hesitation, Ted White requested that a pad be placed behind Peter's head when he was slammed into the shower wall.moviedude345