Continuity mistake: When Tony Gardner is checking the Tiffany doll (right before it grabs his crotch), he puts both knees on the ground right before the shot ends. In the next shot, only one of his knees is on the ground.
Continuity mistake: When Glen has his first voiceover at the ventriloquist show, when he says, "I'm not like that at all," there's a small hair stuck to his face near his left eye. It disappears in the very next shot where you see him.
Continuity mistake: When Psychs the ventriloquist goes on stage, in the first shot, he doesn't have a cigarette in his mouth. In the next shot, one appears in his mouth. He has his arm extended in both shots, so while he is briefly off camera for about one second, he wouldn't have time to put the cigarette in his mouth, then re-extend it between takes.
Revealing mistake: When Glen enters the child's room in the dream sequence, look out the window behind the rocking horse. There's an odd, unnatural stream of water firing diagonally among all the rain. (Likely some sort of flub with whatever sprinkler system they're using to create the rain on the windows.)
Factual error: When Glen kills the mother in the dream sequence, you can pretty see the mother's pulse in her neck still, even though she's supposed to be dead.
Revealing mistake: When the mother slips and falls out of the bathtub, there's a very clear jump-cut while the camera is facing the side of the bathtub. Instantly between cuts, the pattern of the water droplets changes, even though it's supposed to all be one continuous, unbroken shot. This reveals that it was pieced together from multiple different takes.
Revealing mistake: When the father gets stabbed in the dream sequence and falls over the railing, you can tell there are multiple jump-cuts in the shot, even though it's meant to be one continuous, unbroken shot. It's especially noticeable when he lands, and several broken pieces of wood simply "appear" around him between frames.
Other mistake: During the opening dream sequence, as Glen begins to walk through the house, you hear it raining outside and can see rain outside the windows, except the front door windows, which show absolutely no rain whatsoever.
Answer: Have you ever SEEN demon doll DNA? It's creepy! Not at all like your 'normal' DNA. Now, if you have a Barbie and Ken doll having a kid, you'd get something nice like a P.J. Doll. You mix evil, twisted, Chucky with psychopathic Tiffany and all bets are off, baby-wise. I'm surprised that Glen turned out as well as he did! And with a Cockney accent?
CCARNI ★