It's the kind of thing that once you see it, you never forget it. Secret messages like the arrow in the Fed Ex logo or the 31 in the Baskin Robbins logo or the arrow point from A to Z in the Amazon logo.
Another example of a message in a mark was one I designed while Creative Director at Evenson Design Group working with the LaBrecque team. As the story goes, Reading Cinemas transformed from a family owned railroad (as in Reading Railroad from the Monopoly game) into entertainment complexes including the Angelika Film Center in NYC. You will see the railroad forming into a filmstrip in the R shaped mark to tell that story.