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)
Visible crew/equipment: When Julie says "It's probably just your nerves" then Heather replies "Nerves?!", above Heather's head you see a boom mic dip down into view. (00:12:25)
Visible crew/equipment: When Heather is leaving to go to her TV show, she and Julie walk out Heather's house. As they walk out and talk, you can see a boom mic dip down into view for a while. (Seen on DVD version) (00:13:25)
Visible crew/equipment: When on the phone to Chase, Heather says "He's had some sort of an ... episode" and as she says this a boom mic briefly dips into view, above her head. (Seen on DVD version) (00:23:40)
Visible crew/equipment: The boom mic dips into view once again whilst Heather is on the phone to Chase, as she says "...Like Freddy." (Seen on DVD version) (00:24:00)
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)
Revealing mistake: When the glove comes up the car seat and into Porter's chest, there are lights from buildings out the side window, so the car isn't moving at all. When it cuts, there's suddenly a hill where the lights should be and now the car is moving again. (00:29:30)
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)
Factual error: When Dylan wakes up in the hospital, under a plastic tent, we hear the iconic "flat-lining" sound of a heart monitor. Dylan then removes the clamp from his finger and the sound stops. The clamp is an oximeter, a device that measures blood oxygen concentration. The wires going under his shirt are the heart monitor. The sound should not have stopped. (01:12:42)
Visible crew/equipment: The boom operator for this film should have been fired. You can the microphone dip into view whilst Dr. Heffner is whispering to her junior nurses, as you can hear Heather wrestling with the security officers. (Some DVD versions.) (01:14:00)
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)
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.