Continuity mistake: In the flashback when Peter fights Ernie the Giant Chicken, Peter gets knocked off the top of an eighteen wheeler and grabs the second rung at the bottom of the truck's ladder. But when the truck driver sees the pair in his side view mirror, Peter is hanging off the top of the ladder. (00:02:00)
Audio problem: When Peter introduces the pope to his friends at work, and he is saying "Remember when we got that stripper for Charlie and it turned out to be his son? I think this is gonna top it" or something along those lines), Peter's mouth very obviously does not sync up with the words being said.
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. (00:11:40)
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: When Peter enters the cockpit and accidentally kills the pilots the cockpit looks small enough so that it could only fit Peter and the pilots in their seats. However, when he turns around to leave the cockpit looks big enough to fit an entire group of people.
Continuity mistake: After Lois accuses Stewie of peeing on the carpet, he asks her to bend down and slaps her with a glove. The glove remains in his hand in that cut, is still there when there is a wide shot of Peter, Stewie, Lois and Brian (you can just see it next to his trousers in his hand), but when it cuts back to Stewie and he starts on about "the outrages" etc, it is gone (the cut is instant, no time for him to put it back in his pocket). A common error, this one just struck me as strange, because the sandwich Stewie threw at Lois is there the entire scene. (00:03:35)
Continuity mistake: When Ulysses S. "Griffin" is chugging beer with Robert E. Lee, Ulysses wins. When he says "How's that Robert E. Lee," he puts the beer glass on his head. After Robert says, "Okay no more slaves, but we still don't have to read books," the glass is in Ulysses' hand. In the next shot it's on his head again. (00:10:05)
Continuity mistake: In the scene where Lois goes down to the room where Peter is dancing, Peter is wearing blue pants. After he walks over to the door and greets her, he still has blue pants. The next shot of Lois and Peter dancing has him wearing his normal green pants, but after that it goes back to blue pants for the rest of the scene. (00:11:35)
Continuity mistake: When Karen Black is first shown, her blue uniform is sleeveless, showing her white shirtsleeves. After a cut to the "Dawson's Creek" kids, Peter says "It was a movie in the seventies," and Black's outfit has sleeves. Later, when she is helping people off the plane, her uniform once again is sleeveless.
Continuity mistake: The position of the hole on the leg of Meg's pants changes. In the scene where Meg is putting the mouse traps around Joe, the hole is on the right side. When they arrive at the house with Randy Newman and Meg is telling Peter that the Twinkee factory in Natick may not even exist, the hole is on the left side. This happens again throughout the episode. (00:10:55 - 00:12:30)