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: During the final chase scene where Melanie 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 her co-worker is found murdered. (01:08:50)
Continuity mistake: When Demon is in the outhouse, the pullcord hanging above his right shoulder disappears in some shots. (00:51:35)
Continuity mistake: When Joey walks out onto the porch, he has a yellow chocolate bar sticking out of his sweater. In a following closeup it has gone but it reappears in the next wide shot. (00:17:20)
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)
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: 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: After Eddie scares Tommy with the mask, on the wall there's a poster - "Four ways you can stop drug abuse...", with nothing under it. When Tommy beats Eddie up there's now another small sheet tacked up under it. (00:29:45)
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)
Trivia: There are three different hockey masks used either in this film or its advertisements. The first is the one that the Jason impostor (Roy) wears. It has two blue triangles below the eyes. The second is the one the real Jason wears when Tommy sees him in the hospital room at the end, with the red triangles. The third is featured on the poster. It has an un-holy amount of breathing holes on it. (01:23:00 - 01:27:10)
Revealing mistake: When Pete gets his throat slashed, you can plainly see that there's no actual cut, it's just a line of stage blood. (00:26:30)
Continuity mistake: In the film Tommy tosses the alien mask that he wore to scare Reggie on his bed and the mask slides down the wall and is all crinkled up. In the following shots Tommy takes out another mask and you can see the alien mask now laying flat on his bed and away from the wall. (00:13:10)
Continuity mistake: While Eddie is being killed, in the second shot, there's a blood driblet on his bottom lip. In the next shot, his bottom lip is clean without any blood residue.
Continuity mistake: When Demon is in the outhouse and the wall is speared the first time you can see the pike coming in above the toilet paper roll. When it cuts the pike is almost below the roll. (00:53:15)
Answer: Yes, originally Tommy was going to be the new Jason. But the makers decided to go in a different direction for part 6.