Revealing mistake: Healy tears off the October 26 sheet from the calendar, and before the camera cuts away, it shows the October 25 sheet underneath it. That's not how calendars work. (00:11:25)
Revealing mistake: When doing the blindfold dare, the same clip of them swerving between cars is used 2 or 3 times. (00:44:10)
Revealing mistake: When Fujiwara is about to have sex with Hideko, there is a shot with Hideko in the foreground of the shot, kneeling on her hands and knees and Fujiwara behind her kneeling down on his knees whilst holding onto her with his left arm. Fujiwara is shown removing his trousers using only his right hand, but it is apparent that he is just miming the actions of removing his trousers before throwing them on the floor. Attempting to remove a pair of trousers with only one hand would be extremely difficult and if he is kneeling on the floor, it would require him to lower the trousers down to his knees, lift his knees off the ground, pull the trousers around the knees and then fully pull them off his lower legs. While not impossible, this would be very hard to do, but he manages to do this in just a few seconds with almost little to no struggle. (02:02:53)
Revealing mistake: When the Creature is telling Louis the "Bat Story," the Creature is holding a burning torch in its right hand against a wholly-dark background. It becomes apparent that the shots of the creature are actually Dutch Angle shots (the angle of the camera is rotated about 45°), because the smoke from the torch is not rising straight upwards; rather, the smoke is rising at a 45° angle toward the upper left corner of the screen.