During "Rapid Start" engagements with folks from MongoDB Inc., some sample MongoDB documents with "fake" data are often generated using a handy little set of utilities called mtools.
This type of utility is very useful, particularly for generating fake data for testing data validation logic. The utility was developed by an engineer out of the MongoDB Inc. New York City office.
A nice summary report from the "Rapid Start" sessions is typically delivered to the client, and a brief mention of the mtools fake data generator usually appears on the final pages of the PDF, including the fake data "template" used to generate documents. This template could easily be adapted for data validation testing.