Near the end, in one shot, the Griffin's station wagon is blue, not red.
At the end, the plates of food simply disappear from the picnic table.
During the construction of the float, the buttons on Peter's shirt change sides in one shot.
At the end of Love Thy Trophy, The Griffins and neighbors are eating outside and they discuss the mystery of their trophy. Brian tells the table that it caused to many problems and is probably better left lost. Various members of the table chime in agreeing. One of them is Bonnie who, although agreeing with Brian's statement says, "Peter's right."