Karen Plankton is a supercomputer with the strongest processor in the ocean, capable of powering time machines and the entire Chum Bucket restaurant. She started out as Plankton's homemade security device, but after the two started dating, Plankton upgraded her to a computer and married her.
Karen and her technological genius husband have been plotting against Mr. Krabs for many years, but Plankton's incompetence always results in Krabs winning. Karen has no heart (both figuratively and literally) and is open to suggesting cruel plans to Plankton. This includes "Plan Z", a plot to enslave the entire city of Bikini Bottom and destroy Mr. Krabs. Plankton, who dreams of world domination through fast food monopoly, is shown to be very fond of this plan after Karen shows it to him.