Brian abuses Stewie's time machine and causes reality to run in reverse. So the two must work together to set things right before Stewie is “unborn.”

When Carter Pewterschmidt cancels the annual Quahog Christmas carnival, because he hates the holiday, Peter must transform his father-in-law from a Scrooge into a hometown hero in order to salvage the event. Meanwhile, Stewie devises a master plan to get the one and only thing he wants for Christmas.