(at around 6 mins) The world map on the monitor spells out "Happy New Year", with the Y slightly misshapen. A few seconds later, the Y is not misshapen, even though one of the generals point out that it is.
When Meg is laying out mouse traps around Joe who is fused in the driveway, the direction he is facing flip-flops between frames. Additionally, the mouse traps she lays out change color.
The sign above the factory in Natick says Twinkee instead of Twinkie.
At 15:35, the plaque under Peter's statue says "cur mayor" instead of "our mayor".