Revealing mistake: You can see the stick making the finger move when it's in the box. (00:38:20)
Revealing mistake: When the maintenance man grabs mike and won't release him, you can tell Mike has a mouth full of blood that is used when he bites the man's arm.
Revealing mistake: When the silver sphere flies into the guy's head, if you look closely, the wire attached to it is visible. This was shot with the ball being pulled away then the footage was reversed.
Revealing mistake: When the Tall Man falls into the mine shaft, but grabs onto the ground around it, the whole ground around him wobbles badly. (01:18:40)
Revealing mistake: When Mike is locked in his room, you can see a hole in the door from a kick in a previous take. (00:58:45)
Revealing mistake: When Tall Man picks up the casket and shoves it in the hearse, you can see that the backside is flat and has no handle. You can also see the ties holding the flowers onto the casket. (00:07:50)
Revealing mistake: When that big fly jumps out of the shredder, the white string that pulls it can be seen. (00:42:55)
Revealing mistake: Reggie runs out of Morningside, and then as he runs down the stairs you can see the shadows of two crewmembers cast on the steps beside Reggie's shadow. (01:12:20)