When Stewie is promoting the book, "Everybody Poops," a purple book on the table disappears between shots.
In the cutaway gag showing the "invention" of the Reese's peanut butter cup, Officer Reeses arrives at the scene of a car crash and moves to take driver #2's jar of peanut butter with chocolate in it, but then holds up and takes a bite from driver #1's peanut butter-covered chocolate bar.
When Brian comments about Stewie reading a book promoted by Oprah, he says he can see her "giant" sticker on the book. A few seconds earlier, when Stewie showed the book's cover to Brian, there was no sticker on it, just a very clear title.
During the "Freakin FCC" musical number, when Stewie gets flushed down the toilet, he spins counter-clockwise, something that only happens south of the equator.