Enter these in the Unlock Codes screen in the options menu.

Password	Effect
Technus, Jimmy, traloc, Plankton	Colorless enemies
Beautiful Gorgeous, Zim, Plankton, Technus	Enemies in blue
SpongeBob, Tak, Jimmy, Danny	Enemies in red
Dib, Plankton, Technus, Jimmy	Extra attack
Zim, Danny, Plankton, Beautiful Gorgeous	Extra defense
Plankton, Beautiful Gorgeous, Technus, Traloc	Hard bosses
SpongeBob, Dib, Dib, Technus	Hard enemies
Tak, Traloc, Jimmy, Beautiful Gorgeous	Infinite health
Dib, Tak, Beautiful Gorgeous, Plankton	Instant KO
Plankton, Tak, Beautiful Gorgeous, SpongeBob	Invincible partner
Danny, Beautiful Gorgeous, Jimmy, Technus	Items +
SpongeBob, Traloc, SpongeBob, Danny	Items ++
Plankton, Dib, Beautiful Gorgeous, Plankton	Max defense
Tak, SpongeBob, Technus, Danny	No health items
Traloc, Zim, Beautiful Gorgeous, SpongeBob	Prices down
Beautiful Gorgeous, Technus, Jimmy, Beautiful Gorgeous	Super Beautiful Gorgeous
Danny, Zim, Danny, Beautiful Gorgeous	Super Danny
Zim, Plankton, Dib, Plankton	Super Dib
Beautiful Gorgeous, Traloc, Jimmy, Jimmy	Super jetpack
Technus, Danny, Jimmy, Technus	Super Jimmy
Tak, Plankton, Dib, Technus	Super Plankton
Technus, SpongeBob, Technus, Traloc	Super SpongeBob
Danny, Jimmy, Tak, Traloc	Super Tak
Danny, Technus, Tak, Technus	Super Technus
Traloc, Beautiful Gorgeous, Dib, SpongeBob	Super Traloc
Plankton, Zim, Technus, SpongeBob	Super Zim