Continuity mistake: In the first shot of the flashback showing the family watching "Philadelphia," Peter's eyes are about twice as big as they normally are due to the Irish coffee, but are instantly back to normal in the next shot.
Family Guy Viewer Mail #1 - S3-E21
Continuity mistake: When Lois is saying "We each seem to have acquired superpowers.", her size in relation to the chair in front of her changes between shots.
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: In the flashbacks to 1984, Peter and Lois are both 18, but in a previous episode, Lois says that she's two years younger than Peter.
Family Guy Viewer Mail #1 - S3-E21
Continuity mistake: When the 'Knight' and the 'Ghost' bump into each other in the corridor, the armour and bedsheet fall on the floor, but in the next shot, the armour and bedsheet are gone. (00:18:40)
Continuity mistake: When Lois, Meg, Chris and Stewie first enter the courtroom there is a brown-shirted man sitting next to Quagmire. In the next shot, there is a pink-shirted man there. (00:18:25)
Airport '07 - S5-E12
Continuity mistake: When they are on the Redneck Tour, when we first see Peter talking, the man behind him has a mustache. As the camera zooms in closer to Peter, the man is suddenly clean shaven. There are several other changes with people behind the Griffins, between shots. (00:00:55)
Continuity mistake: In the flashback when Peter fights Ernie the Giant Chicken, Peter gets knocked off the top of an eighteen wheeler and grabs the second rung at the bottom of the truck's ladder. But when the truck driver sees the pair in his side view mirror, Peter is hanging off the top of the ladder. (00:02:00)
Halloween on Spooner Street - S9-E4
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: Osama bin Laden's dialysis machine disappears after Stewie knocks him down. (00:02:30)
Continuity mistake: When Stewie first discovers Lois and Meg spying through the peephole, the peephole is too high for Stewie to reach, but when Stewie walks up to the peephole, it is low enough for him to look through.
Continuity mistake: After Joe shoots a hole in the table, the hole changes size. (00:02:00)
Continuity mistake: When Peter says he's gonna buy his family the biggest meal they've ever had, Stewie's eyes are drastically bigger than usual. (00:13:15)
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.
A Very Special Family Guy Freakin' Christmas - S3-E16
Continuity mistake: When Peter is driving, Quagmire is sitting beside him and Cleveland and Joe are in the back seat. Joe has brown hair and he's wearing a gray knit hat and a light coat with a gray fur collar. When Quagmire is sticking his body out of the car door and yelling "Whooooooa! Whoooooooa!", look at "Joe" in the back seat. Joe doesn't look like Joe in this shot. He's wearing a Santa hat and a brown coat just like Quagmire's, and a bit of his hair is also black like Quagmire's, instead of brown. (00:05:30)
Family Guy Viewer Mail #1 - S3-E21
Continuity mistake: When Lois picks up the fridge there is nothing stuck to the fridge but when she puts it down there is a note stuck to it. (00:09:40)
Jungle Love - S4-E13
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: The English guy's car is full of crates when we first see it and when his roof is blown off but after Peter and a crewman have boarded, there are suddenly barrels in the car too.