Kevin Greutert was initially hired to helm the film but was forced to work on Saw 3D: The Final Chapter (2010) when the producers of that film exercised a clause in his contract, forcing him off Paranormal Activity 2 (2010).
When Ali finds the scratches on the cellar door it is on a four panel door. When Dan goes down into the cellar and turns to look at Ali at the top of the stairs the door is completely different to the one seen before.
When Kristi is alone in the kitchen then all of the cabinet doors open at once, she then runs from the room and the cabinet doors are all closed, when she runs back in to turn off the burner the doors are still closed, but when she goes back in to clean up the doors are all open and the stuff that fell out of the cabinets is till on the ground in the way of the doors so there is no way they could have closed earlier.
It wants Hunter. It is explained in the movie that Kristi's great-grandmother made a deal with a demon for wealth and power. Payment is to be forfeiture of the next firstborn male child. If the debt is not honored, the demon will follow her brood until the soul of a male infant is collected. Hunter is the first male to be born in the family line since the deal was made.
Q
A Note Regarding Spoilers
A
The following FAQ entries may contain spoilers. Only the biggest ones (if any) will be covered with spoiler tags. Spoiler tags are used sparingly in order to make the page more readable.
Q
If the demon wants the baby, why doesn't it just possess one of the other 3 family members and take him?
A
It has been suggested that the fear it provokes must reach a certain level before it can possess someone.