In the scene where the men receive the trophy and argue over it, after Quagmire says his line, he doesn't have any teeth. But when Peter speaks again, his teeth are back.
Just before they pan in on the guys from Spooner Street, there's a red, a yellow, a pink and a green/blue baloon. Then they pan in on the guys from Spooner Street and the pink balloon is gone. Then, when they are arguing over who gets the trophy, the pink balloon is back.
While everyone meets at the Griffin's for Peter to ransack their houses, the Griffin's living room changes between blue and yellow.
During the scene where Peter and Lois confront their neighbors about how Stewie was taken away, while Lois is talking, the Griffins' station wagon is blue, but when it shows the rest of the neighbors and any other scene containing the car, it is the usual color, red.
When Meg shows off her new Prada bag, the flap design changes from an upside-down triangle to one right side-up