As revealed by DVD commentary, the Korean animators often draw books to read right to left instead of left to right.
Peter falls through the stairs and is trapped. Next he is in the bedroom having splinters removed with Meg complaining, when we pan down to the slumber party the stairs are intact.
At the end of the episode, when Peter is holding the Bible, the title of the book is on the wrong side. This is because the show is animated in Korea, where they read right to left, rather than left to right. Mentioned on the commentary.
While walking into Quagmire's kitchen, Meg's toothbrush disappears from her left hand in one frame.
When Peter puts on the Reagan mask, Chris is seen laughing, but cannot be heard doing so.