Area 51 Hat:
Get to level 3-1.
Blond Hair:
In the Options Menu, where you can rename your alien, enter Cletus.
Daisy Headdress:
In the Options Menu, where you can rename your alien, enter Princess or Betty.
Diamond Tiara:
In the Options Menu, where you can rename your alien, enter Abe.
Dick Tracy hat:
In the Options Menu, where you can rename your alien, enter Dandy.
Jouster Hat:
Beat Level 3-4 using hard difficulty.
Minigames, Levels and Hats:
Set the player 1 name to ROYGBIV.
Pirate Bandana:
In the Options Menu, where you can rename your alien, enter Goodman.
Private Eye Hat:
Beat Level 3-2 using hard difficulty.
Red Hair:
In the Options Menu, where you can rename your alien, enter April.
Soviet Union Hat:
Get to level 2-1.
Super Soviet Missile Master mini-game:
Finish level 1-5 and the Super Soviet Missile Master mini-game will be unlocked after the intermission sequence.
Top Hat:
In the Options Menu, where you can rename your alien, enter Grrl.