There is a bounus/secret mission in StarCraft II: Wings of
Liberty. To unlock this secret mission you need to find a document in a mission called Media Blitz.
This is the mission where you get to expose Emperor Mengsk's dirty little secret. To find the document, get some units to the
lower right part of the map. Find the science facility then destroy it. A
document will drop out then you need to pick it up using one of your units.
Doing this will unlock a new mission in the Starmap.