Continuity mistake: When Diane falls in the pool, the distance to the floating corpse on the left increases or decreases randomly depending on the shot.
Continuity mistake: After Carol slides through the kitchen floor, Steve rests with his back against the wall, over a brown line. When the angle changes, a frame later, he's resting half a meter to the right of the line.
Continuity mistake: While Diane faces the creature and demands it not to touch her babies, she is resting against a long flat wall, but from the angle behind, half of her body is resting against a corner.
Continuity mistake: The night the clown attacks Robbie, when he turns off the light the lamp and the Darth Vader bust swap positions between shots.
Continuity mistake: Before the clown attack, its left leg keeps changing positions between shots.
Continuity mistake: The night after burying the bird, Robbie's hat is not tucked in, however a frame later it's totally tucked in.
Answer: Ectoplasm.
Phixius ★