Revealing mistake: During the scene when the people at the pool think Chris is a car sitting on the diving board, just before Lois moves out of the shot before the scene changes, her lips disappear for a split second. It's really fast but still easy to notice even without pausing or slow motion.
Continuity mistake: In the scene where Stewie is eating chocolate cake, he shoves his head in it and covers himself in cake. However when Peter walks in after having liposuction, all the cake has disappeared and Stewie is now completely clean. The bowl of grapes on the table is also gone.
Continuity mistake: Just before the pest control team leaves for the Griffins', we see the black team member holding a shotgun in his hand. After showing Logan in shot, it returns to the black member and he's now holding what looks to be an MP5 machine gun. In the following shot as he starts to slide down the pole, the gun is once again a shotgun.