Revealing mistake: When Ernest runs away from Lisle, after he nearly drinks the live-forever potion, he runs down a hallway and commences to open a door with a doorknob on the left side of the door. It then cuts to the other side of the door, of Ernest walking through the door (into the party), and now the doorknob is also on the left side of the door, but it should be on the right side. (01:21:35)Hamster
Revealing mistake: Towards the end when Helen is about to fall down the stairs of the church (pulling Madeline with her) you can see the rope between her legs that is keeping her in the tipping point position. (01:36:55)
Revealing mistake: When Madeline is at Lisle's place the first time, she has to sit on a couch, next to a young man. Lisle tells him to make room for Madeline. He stands up and you can see a transmitter on his back attached to his pants.