The Hand That Rocks the Wheelchair - S9-E12
Continuity mistake: When Stewie spots "evil Stewie", the evil clone is off the carpet and next to the hi-fi. In the very next shot he's moved far closer to Stewie and Brian.
The Hand That Rocks the Wheelchair - S9-E12
Continuity mistake: Meg drops Joe's gun into Bonnie's bag at the airport, but it's zipped closed - you hear the baggage check guy unzip it before looking in it.