Continuity mistake: Just before Peter enters the tunnel in his new car, the white line in the middle of the road is blotchy and not continuous. When the shot changes to Peter's POV, the line has completely disappeared. The next shot which shows the car side on, there is now a straight white line on the road.
Continuity mistake: When the flag team first walks out to the field, they are all in a straight line. Next time they are in two seperate lines with Meg at the head. Also, the girl with the head brace moves to the front when she is seen in the back. There is not enough time for them to move into the lines.
Continuity mistake: As Stewie is about to eat his brisket (just before he throws it at Meg) he is cutting part of it off. Just as he cuts through the shot cuts and you can see the brisket is now back in one whole piece. You can also see the mashed potatoes change from white to green.