SQL Server Database "default" tables
This happens (based on the discussion in comments) because the tables exist in the model system database. As per the documentation (my emphasis):


  If you modify the model database, all databases created afterward will
  inherit those changes. For example, you could set permissions or
  database options, or add objects such as tables, functions, or stored
  procedures. File properties of the model database are an exception,
  and are ignored except the initial size of the data file.


As a solution, dropping the tables from model will stop this phenomenon.