In the scene where Don Knotts appears the family portraits on the kitchen wall disappear, and the open door moves closer to the passage to the dining room.
When Lois is consoling Jerome after his house burns down, Peter says, "This whacked-out world. It just makes you want to grab your nephew and get in a van and shoot people in the DC area." The reference is to John Allen Muhammad and Lee Boyd Malvo, who killed 10 people in a series of sniper attacks in October 2002, a crime for which Muhammad was later executed. Though initial eyewitness reports suggested that a white van was seen at the sites of the attacks, the reports proved to be erroneous and the snipers were in fact driving a Chevrolet Caprice sedan. Also, Malvo was a close friend of Muhammad's, not his nephew. However, Peter is a moron, and this was his mistake.
It makes no sense for Jerome to have had "a ton of nasty-ass sex with Meg" while crashing at the Griffins' because that would be a tremendous confidence boost for her and change her entire character which did not occur.
Stewie says that he's watched "Tommy Boy" the day before, and that he he thought Chris Farley had fallen down the hill as a result of Stewie tapping on the glass of the TV. Chris Farley never fell down a hill in "Tommy Boy." The movie referenced was "Black Sheep".