Continuity mistake: After Porter has destroyed the glove controller, the other guy is by the table. The controller isn't there, but when it cuts, he is suddenly by the controller throwing it to the floor. (00:03:30)
Continuity mistake: When on the phone we hear Freddy say "Freddy's comin for you!" Heather puts the phone down, but it doesn't go on the hook. Yet when it cuts to Dylan standing in the kitchen, the phone is back on the hook. (00:10:10)
Continuity mistake: When Julie puts Dylan down and Dylan says "Mommy, stay home then", between shots Julie goes from having her right hand on her hip, and her left arm down by her side, to having her left hand on her hip and her right arm down by her side. (00:11:55)
Continuity mistake: When Nancy asks Dylan "What is that?" and Dylan answers "Rex," the book is on the bed. When they crawl under the sheet, the book is gone. (00:26:20)
Continuity mistake: When we see Porter through the windshield of his car, there is no blood on his shirt. When it cuts, the shirt is covered in blood. (00:29:35)
Continuity mistake: After Heather discovers the long scars on Chase's body, she turns to be sick. In one shot, she has her hand by her mouth, then when the shot changes her hands are down by her side. (00:33:45)
Continuity mistake: At the hospital when Nancy says "Dylan, you have to fight it", it cuts during the sentence. First Dylan is looking at Heather, but when it cuts he is looking down. (00:54:25)
Continuity mistake: In one scene Heather is in her room, when the TV turns itself on. She turns it off, then reaches for her coffee jug, and you can see a picture frame by the jug. Yet in the next wide shot of Heather, the picture frame has moved. (01:04:05)
Continuity mistake: When Heather is talking to Dr. Heffner, whilst having her cuts bandaged up, Heather exclaims "I forgot to bring his dinosaur Rex..." After that shot, Dr. Heffner's hand goes from being on Heather's arm, to not, then back on her arm between shots. (01:08:15)
Continuity mistake: Heather goes to the hospital after she is cut by Freddy and the doctor bandages her up. The bandage goes to the middle of her arm then later when she falls into Freddy's world from her son's bed the bandage is around her wrist only and there are no scratches where the bandage should be. (01:08:20 - 01:29:30)
Continuity mistake: While the junior nurse is whispering to Dr. Heffner, "I don't think she ever lets him get a nights sleep." You can see that both of her hands are behind her back, but in the next shot her left hand is up by her neck. (01:14:55)
Continuity mistake: When Julie scares the nurse with the needle, the nurse turns around. When it cuts, she turns around again. (01:15:10)
Continuity mistake: When Freddy is dragging Dylan's babysitter up the wall, you see that no blood goes onto the x-rays on the wall. But in the next shot, you see blood rubbed up the top of the x-ray screen. (01:17:55)
Continuity mistake: When Julie is being dragged by Freddy on the ceiling you see traces of blood where she has been dragged. But there is also blood in front of her where she hasn't been dragged yet. (01:18:05)
Continuity mistake: When Freddy cuts through the sheet before entering reality you see him making a large cut in the sheet. On the next shot, the sheet is only cut in face level. (01:23:50)
Continuity mistake: Heather follows the sleeping pills (bread crumbs) into Dylan's room. She has the pills in her right hand and the kitchen knife in the left. She picks up two pills then reaches for the one on the pillow. She reaches for it with her index finger and thumb her hand closed but when they show the close up on her hand she picks it up with her middle finger and thumb with her hand open. (01:27:20)
Continuity mistake: Towards the end of the film Nancy takes a big kitchen knife to fight Freddy with. When she is falling into Freddy's lair from her son's bed, she clearly has nothing in her hands. However, as she emerges from the water she has fallen in, the knife appears in her left hand. (01:29:10)
Continuity mistake: When Freddy is reaching for Dylan inside the fireplace, his left hand changes position on the bars. (01:34:15)
Continuity mistake: When Nancy is covered with Freddy's tongue, the tongue goes under her shirt. When it cuts, the tongue no longer is under the shirt. (01:36:20)
Continuity mistake: When Dylan and Heather are looking at the manuscript you see them looking at the first page. In the next shot she flips back to the first page again. (01:38:50)
Chosen answer: Mostly just very subtle hints. In the beginning when she arrives right around the same time that Heather gets a call from the psycho-stalker, suggesting a possible connection. And the fact she's alone with Dylan many times during the film, as she could be subtly manipulating him to act out.