Karen Plankton is Plankton's sidekick in the SpongeBob SquarePants television series and theatrical films. She is a self-aware A.I. who serves as the main computer system of the Chum Bucket laboratory. She is the source of Plankton's most successful plots, although he has a tendency to take all of the credit for them. In the third season opener, The Algae's Always Greener, it was revealed that Karen is Plankton's wife. Since then, many episodes focusing on the Planktons have involved their marriage.
Karen is Mark II Surplus UNIVAC with 256 gigabytes of RAM. She was built by Plankton himself out of a calculator, a mass of wires, and a security system. They first met and dated before Plankton became evil.
The further depth of Karen's early life is debatable, since she has two parents. This was first hinted when Plankton told her, "Your parents must have been like, part computer or something." In Single Cell Anniversary, Karen's AI mother is revealed to be EMILP, while her AI father was Fredrick, whom created by a fan and has only been seen in a Nickelodeon Magazine.
Karen normally acts like a nice and loving person when she and Plankton are in a good mood, but she is also evil enough to be a villain (possibly more so than Plankton). In The SpongeBob SquarePants Movie, it is shown that Plankton has a filing cabinet of evil plans that Karen reminds him about. Since she writes the majority of his plans, it can be assumed that she wrote these as well. They are in a descending order from harmless to sinister, the worst being "Plan Z"—the only scheme to result in Plankton successfully stealing the formula and using it to his advantage. This plan involves enslaving everyone in Bikini Bottom, forcing a frozen Mr. Krabs to watch the town descend into evil and be killed by King Neptune, and sending a hitman to murder SpongeBob and Patrick. Karen uses her mind-control abilities to enslave the citizens and is one of the only townspeople not to be a slave. This shows that she is just as cruel and sinister as her husband, if not more.
Her darkest side is also shown in Plankton's Good Eye where she encourages Plankton to be evil and hates his good side. Other instances of her dark side include using her lasers on Plankton in multiple episodes and assisting him in his plots in nearly every story focusing on them.
Being an AI, Karen usually manifests on the large-screen computer in Plankton's lab where she has green facial features. Her face is mostly depicted in the form of a wavy green line. However, she has many other forms since Plankton builds her system into most of his inventions. Her other most common form is a robotic body designed to look like a portable wheeled computer with detachable robot arms.
Oddly, when sprayed by Plankton's baby gas (a special gas that reduces people to a baby version of themselves) she was reduced into a calculator.
Notable Villainous acts
- "F.U.N.": She tells Plankton how to get the formula by using SpongeBob's trust against him.
- "The SpongeBob SquarePants Movie": In one of her most evil roles, she writes and gives Plankton his most diabolical plan yet: Plan Z, which involves enslaving everyone in Bikini Bottom and sending a hitman to kill SpongeBob and Patrick.
- "Enemy In-Law": She nags Plankton and also zaps him with a laser in retaliation of the latter's affair with Krabs' mother.
- "Friend or Foe": She helps Plankton to try to get the formula by pickpocketed it from Krabs' pocket when Krabs and SpongeBob distracted.
- "Krabs à La Mode": She encourages Plankton to steal the formula by using Krusty Krab's frozen state as advantage because simply freeze the restaurant is not enough to run it out of business.
- "Plankton's Regular": Paid a random fish named Nat to eat Plankton's chum to keep Plankton from being sad, in spite of the risk on Nat's digestive system.
- "Single Cell Anniversary": Stealing the Krabby Patty formula as the gift for Plankton in their wedding anniversary. Unfortunately, her undoing in this illegal act was demanding Plankton to give her her own gift, where upon gained what she wanted, Karen was crying so much that she causes her system to overload.
- "Chum Caverns": Upon discovery of underground cave below Chum Bucket, Karen suggested to used the place's scenery to run the Krusty Krab out of business.
- "One Coarse Meal": She does not believe Plankton's claim on Pearl (who is actually Krabs in disguise) haunting him because that "Pearl" only haunted Plankton when she wasn't around.
- "Plankton's Good Eye": She encourages Plankton to steal the formula and aiding him to have a new secondary eye to increase his perception by using SpongeBob's tears. However, Karen's scheme in this backfires as the mutation for creating the second eye resulting unwanted side effect where SpongeBob's persona from that eye began to take over Plankton's mind so she encourage him to despise his good side to restore order on his mind.
- "Walking the Plankton": Upon discovering that Plankton was too absorbed in his obsession in stealing Krabby Patty due to Krabs intentionally sell patties on the cruise ship that they coincidently went on board in their honeymoon, Karen was upset so much that she cleave the ship into 2 with laser, revealing her surprising capacity to suffer Villainous Breakdown in process.