Continuity mistake: When Stewie mentions to Brian about his "Life's a beach" mug, the squares on his calender keep changing size.
Continuity mistake: The buttons on Peter's white shirt switch between the left side and right side, between shots, such as when he tries to play frisbee with James, or when Peter is late for dinner with James.
Continuity mistake: In the episode where Brian and Lois get married, Lois confronts Brian after cheating with Peter back at the house. Stewie is playing with a SIMON SAYS game. Look at the SIMON SAYS when he is playing it (up close), after he is done (the close up shot ends), look at the colors again on the SIMON SAYS, they change.
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: Osama bin Laden's dialysis machine disappears after Stewie knocks him down. (00:02:30)
Continuity mistake: When Chris is saying "I'm not supposed to tell Mom cos she'll just bitch about it" there is a door behind Lois with a box next to it. In the next shot there is a smaller box next to that box which was not there before. (00:09:00)
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)
Brian Goes Back to College - S4-E15
Continuity mistake: After the opening credits, Peter/Hannibal is wearing a jacket with pockets only on his right side; then pockets suddenly appear on his left side between shots. (00:00:40)
Brian Goes Back to College - S4-E15
Continuity mistake: Louis' hand changes places on the newspaper at the start when talking to Brian. Note its position in relation to the column. (00:02:10)