Revealing mistake: When Ethel gets a cleaver in her face, blood spatters everywhere. Yet the cleaver blade is still clean. (00:56:35)
Continuity mistake: When Jake gets a cleaver smacked in his face, you see him get slashed across his face. When Robin goes to bed and she sees his dead body, you can see the slash on his face is in the opposite direction. (01:01:15 - 01:03:30)
Continuity mistake: After watching "A Place in the Sun," Robin goes to her room and removes her blue gown. Then she walks to her mirror, and in the reflection we see the white door at the end of her bed is wide open. In the following shot into her mirror, the door is shut. (01:02:20)
Plot hole: When Robin goes to bed you can see that Jake is not there. When she turns over Roy couldn't possibly have put Jake there in that short time without her noticing, not to mention that she was still awake. (01:03:30)
Continuity mistake: When Violet is dancing in her room, Jason starts to walk up to her and we see the knife has dried blood on it. Then he picks her up, stabs her takes the knife out and now the knife is clean. (01:04:55)
Revealing mistake: Violet has blood on the right side of her shirt before she gets stabbed. (01:05:10)
Continuity mistake: During the final chase scene, where Pam and Reggie are running through the woods, the pink sweater, which is over her shoulders, disappears and reappears at random until she finally loses it by the tree where Matt is found murdered. (01:08:50)
Continuity mistake: When Reggie finds the bodies in Tommy's room, Violet is first propped against the wall, but in the next shot, she is lying down, then she is propped up again. (01:09:00)
Continuity mistake: When Reggie discovers the bodies, blood appears on Violet's face in between shots. (01:09:00 - 01:09:05)
Continuity mistake: As Pam runs through the woods, she stumbles upon Matt with a screwdriver impaled in his forehead. The amount of blood on his face changes between shots. (01:09:25)
Continuity mistake: After Reggie's grandfather flies through the window, his head changes positions between shots. We can also see that he is breathing, even though he is dead. (01:10:10)
Continuity mistake: In the film the killer.aka."not the real Jason" is seen walking through the rain soaked grounds and woods , but yet when he climbs up the ladder at the end of the film his shoes are pretty clean. (01:10:30)
Continuity mistake: Jason chases Pam with a clean machete, however in the shot just before he's hit by the tractor, the machete is bloody. (01:10:40 - 01:11:20)
Continuity mistake: As Reggie rides the tractor towards Jason, his hood keeps changing position, probably in order to cover up the stunt driver's face. (01:11:10)
Continuity mistake: When Reggie hits Roy with the tractor, the wound on his chest only appears after he has hit the ground. (01:11:20)
Continuity mistake: As Jason approaches the smashed barn door, some of the wooden planks in the left side of the door disappear between shots. (01:12:50)
Continuity mistake: Jason gets his left shoulder sliced by a chainsaw. However later his right shoulder can briefly be seen as the one which is cut. (01:17:55)
Plot hole: After Roy is knocked out of the barn doors, Pam and Reggie slowly walk over to look, but then Roy jumps up and grabs onto the barn floor. However when we see a wideshot of him dangling, you can see there are no ledges for him to have gripped onto while he fell, and that it's just a flat wall. Therefore he couldn't have popped up because there weren't any ledges for him to have grabbed a hold of on the wall. He should have instantly fallen on the tractor harrows. (01:18:45)
Revealing mistake: When Tommy is about to slice Roy's arm, you can see that he is not really holding the machete in his hand. (01:19:20)
Continuity mistake: When Sheriff Tucker has the two newspaper clippings he puts the one entitled "Killing Spree End in Crystal Lake" at the top. In the following shot he has the other clipping at the top. (01:21:35)
Answer: Yes, originally Tommy was going to be the new Jason. But the makers decided to go in a different direction for part 6.