When Scott is dancing with the dog, in the shots from inside the cabin, the collar on his shirt is up. But from the shots outside the cabin looking in, his collar is down.
The movie ends with a shot of Mrs. Voorhees old wrinkled head on Jason's shrine. Originally her head was supposed to open its eyes, and smile. Steve Miner comments on commentary how he decided to get rid of the idea, as he felt it would make the movie come across as more cheap and hokey than normal.