In the wake of the sad news coming from Missouri, I thought I'd pass on this tidbit from the American Philatelic Society. Included on their page of fun facts - apparently the Belgians decided to try a animal delivery system involving cats. You will be shocked (shocked, I tell you) to hear that the experiment didn't last long since the cats were "undisciplined". (I'm guessing undisciplined is code for: did not see any good reason to fetch and carry things.) This has apparently inspired a children's book.
h/t to Marjorie M. Liu for posting this link on Twitter.