In some countries, there is a law that toy boxes need to filled with at least a fixed percentage of the total volume of the box. I know Lego addresses this by adding random Lego. At least, I've been assured this during a Lego seminar by a Lego employee (probably community manager) at one of the fanweekend events (Paredes de Coura or Skaerbaek).
However, does anyone have a reference for this, perhaps pictures of what random Lego is added?