Lego filling boxes with random lego to meet law requirements
Not sure if this is a partial answer, but an example is quoted in the act to repeal parts of the Californian (USA) slack-fill legislation:

Toys.  Lego has been sued for slack fill on its "Aqua Zone" building sets.  The boxes which contain the sets are uniform in size, and contain from 29 to 33 pieces, depending on the set.  Each box contains an "actual size" representation of the pieces and a clear and conspicuous disclosure as to the number of pieces.

From: 
SENATE COMMITTEE ON BUSINESS AND PROFESSIONS
BILL NO:  AB 1394
AUTHOR: Figueroa and Senator Richard G. Polanco, 
Chairman      Escutia
As Amended:  9/4/97
HEARING DATE:  September 5, 1997
FISCAL:  Yes
SUBJECT:  Packaging and Labeling:  expansion of exemptions to slack fill laws.