The scene where Kurt Fuller arrives to assess the exorcism victim is a direct copy of the famous scene in the film The Exorcist when the priest first arrives at the townhouse.
When Kristen arrives at the Hopkins house for the exorcism, there is a sign on the door apologizing that they don't have any candy because they are, of course, very busy. When David steps outside after the exorcism, it can be seen that the house is covered in toilet paper from unhappy trick-or-treaters.
This is the first episode which the number in the title is not a multiple of three.
When David steps outside after the exorcism, the Three Stars can be seen in the sky above him.