Karen is seen in two forms (a large supercomputer on one wall of Plankton's laboratory, and a wheeled computer). In both forms, she is mainly a blue-bordered black screen with a neon green line that moves whenever she speaks.
Karen is shown to be less antagonistic than her husband Plankton, but nonetheless a villain. She often comes up with Plankton's plans to steal the Krabby Patty secret formula (which Plankton usually takes the credit for).
Most promotional images of Karen are based on her appearance in The SpongeBob SquarePants Movie, in which she is almost entirely gray. She never appears like this in the show itself.
Several toys of Karen have been produced, such as a LEGO piece exclusive to the "Chum Bucket" set and a figure included in the Krusty Krab Imaginext playset.