Continuity mistake: When Peter is calling for people to fight Lois, he is standing next to a sign that says "Fight the ass kicking housewife" and has metal rings at the top. When it moves to a closer shot, a hyphen has appeared between "ass" and "kicking". Then, after the space where the commercial break would have been, the sign now says "$10.00" and there are no metal rings. Finally, in the next shot, the sign says "Fight the..." and has metal rings on top. (00:06:55)
Continuity mistake: When we first see Joe's police car in his driveway, the lights on top of the car have the blue half on the driver side and the red half on the passenger side, later on in some scenes the red half is on the driver side while the blue half is on the passenger side.
Continuity mistake: When the Griffins are driving to Washington we see a faraway shot of the car driving from left to right. Peter and Lois are in the front and Chris is leaning back on the back seat. In the next shot, Chris is leaning forward against the back of Peter and Lois's seats. (00:19:30)
Continuity mistake: When Peter enters the cockpit and accidentally kills the pilots the cockpit looks small enough so that it could only fit Peter and the pilots in their seats. However, when he turns around to leave the cockpit looks big enough to fit an entire group of people.
Continuity mistake: In series 4 episode 13 Jungle Love: When the family are escaping the tribespeople, Chris is wearing the tribal clothing. When they jump in the plane there is a brief far-off shot of Chris wearing his usual cap and t-shirt. In a close up shot moments later, he is wearing the tribal gear again.
Continuity mistake: After Lois accuses Stewie of peeing on the carpet, he asks her to bend down and slaps her with a glove. The glove remains in his hand in that cut, is still there when there is a wide shot of Peter, Stewie, Lois and Brian (you can just see it next to his trousers in his hand), but when it cuts back to Stewie and he starts on about "the outrages" etc, it is gone (the cut is instant, no time for him to put it back in his pocket). A common error, this one just struck me as strange, because the sandwich Stewie threw at Lois is there the entire scene. (00:03:35)