Character mistake: On the mailbox where Linus delivers his letter, on the side of the Mailbox is written "U.S Mail." That should be on the letter, not the mailbox. There should also be a period after the S making it U.S. Mail.
Character mistake: When Simon Dermott, a world-renowned museum security expert, steals the fake Cellini statue from the stand, he replaces it with a wine bottle, carelessly leaving his fingerprints all over the glass.