To enter the codes you must go to the large screen in the main area and go to the sub screen that looks like a mystery detective shuushing you..

Password	Effect
Spongebob, Beautiful Gorgeous, Danny, Plankton, Technus	Allows you more time for gadget combos.
Traloc, Plankton, Danny, Plankton, Tak	Coins are attracted to you making it easier to aquire great wealth.
Danny, Danny, Danny, Technus, Technus	Goo doesn't slow you down and you can jump while in it.
Plankton, Jimmy, Beautiful Gorgeous, Jimmy, Plankton	You won't lose coins when you're knocked out.
Jimmy, Technus, Spongebob, Tak, Technus	Your gadget meter will always be full.