Revealing mistake: When Jesse is cleaning out his room, he puts a tape into his tape player, and presses a button down on the top of it. But halfway though the scene of him packing his things away, you can clearly see the button is no longer pressed down, yet the tape still plays. (00:18:10 - 00:19:00)
Revealing mistake: When the bird is flying around acting crazy, both lamps get knocked off the tables, yet the room stays lit up.
Revealing mistake: Freddy bites Lisa on the leg. When she starts to kick him, you can see it's Lisa's stunt double.
Revealing mistake: At the end of the film, Jesse and Lisa react way too early to Freddy bursting out of the girl sitting behind them. (01:18:52)