Select the 'Media Blitz' mission and destroy the lone red building situated on a small floating platform at the far right side of the map. Their is a pathway to this building from the small enemy expansion base that is found just north of your starting position which is marked as a civilian building when hovered over. When this building gets destroyed 'secret documents' will appear. Collect them with a ground unit to unlock the secret mission which will become accessible through the Starmap when you have completed the current mission. You will not be able to play the secret mission after going to Char. You must go to the 'Load' menu and load a game from before Char in order to play the secret mission.
Using 'Control Group' select ALL the queens. Then hold 'Inject Larvae' and press 'Backspace' to jump between each hatch and click that hatch. Doing this will use the closest queen to cast 'Inject Larvae' without having to press 'Inject Larvae' each time.
During gameplay press 'Enter' to bring up a message prompt and then type in the following case sensitive codes without the quotes to enable the corresponding effect. Enabling the following codes will prevent achievements from being earned until a new campaign is started or a saved game before codes were used is loaded.
Gives 5,000 Credits: Type 'whysoserious'
Invincibility: Type 'terribleterribledamage'
Units No Longer Cost Resources: Type 'moredotsmoredots'
Disable Victory Conditions: Type 'tyuhasleftthegame'
5,000 Gas: Type 'realmendrilldeep'
Resources Granted: Type 'jaynestown'
+1 Weapon, Armor, and Shield Upgrade: Type 'iamironman'
Disable Tech Requirements: Type 'sosayweall'
Disable Ability Cooldown: Type 'hanshotfirst'
'Terran up the Night' Song: Type 'overengineeredcodpiece'
Enter the following codes (without the quotes) in the chat box during the Lost Viking mini-game to enable the corresponding effect. To bring up the chat box press 'Enter' during gameplay. The dashes that precede most of these codes must be entered as well.
Add Indicated Points to Score: Type '-score (number)'
Extra Life: Type '-ADDLIFE'
Alternate Background: Type '-mb'
Level Skip: Type '-LEVELCLEAR'
Display 'Boss Incoming' Message: Type '-ss'
Display the Sine of Three Angles:: Type '180', '90', and 'pi sine'