Continuity mistake: Penny's letter to Desmond changes as he reads it. The text stays the same, but the handwriting and position of the words on the page change between the two shots where you can see the letter from the front. Also, for the audience the letter is read aloud with Penny's voice. Interesting is the fact that there is one sentence omitted: "Sorry to be so dramatic, but these are dramatic times, are they not?" (You can read this sentence in both "versions" of the letter though).