Plankton: 1% evil, 99% hot gas.
~ Karen's scan of Plankton.

Karen Plankton is one of the main antagonists of the SpongeBob SquarePants television series and its theatrical films, along with her husband Sheldon Plankton. She is a self-aware A.I. who is Plankton's sidekick and serves as the main computer system of the Chum Bucket laboratory. She and Plankton are constantly scheming to steal the Krabby Patty formula from Mr. Krabs. Karen is typically the brains of the operation, coming up with complex plans to run Krabs out of business. However, Plankton has a tendency to take all of the credit for her ideas.

Karen and Plankton first appeared in the episode Plankton! from season one. 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.

She is voiced by Jill Talley.


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 a software program named EMILP. Her father is an outmoded computer named Fredrick, who has so far only been seen in an issue of 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 that made its debut in Friend of Foe.

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.

Villainous Acts

  • "F.U.N.": She tells Plankton how to get the formula by using SpongeBob's trust against him.
  • "Plankton's Army": She helps give Plankton the idea to recruit his family members to take down Mr. Krabs.
  • "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 zaps Plankton with a laser after his affair with Krabs' mother.
  • "Friend or Foe": She helps Plankton to try to get the formula by pickpocketing it from Krabs' pocket when Krabs and SpongeBob were distracted.
  • "Krabs à La Mode": She encourages Plankton to steal the formula by using Krusty Krab's frozen state as advantage because simply freezing the restaurant is not enough to run it out of business.
  • "Plankton's Regular": She 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.
  • "Plankton's Good Eye": She reveals that she loves Plankton's evilness and doesn't want him to become a good guy.
  • "It's a SpongeBob Christmas!": Karen analyzes SpongeBob and finds out that he is immune to jerktonium, leading Plankton to create a wind-up robot sponge to ruin SpongeBob's chances of getting presents from Santa.
  • "Evil Spatula": She unknowingly tries to make faux Krabby Patties out of the recipe SpongeBob gives his talking spatula, which ends up being a trick from Mr. Krabs.
  • "Plankton Gets the Boot": She kicks Plankton out of the Chum Bucket after he insults her screensaver and is mean.
  • "The Legend of Boo-Kini Bottom": She hosts the Chum Bucket's "Horrors of the Krusty Krab" show, which spreads lies about the business practices at the Krusty Krab.



           Nickelodeon Movie Villains

Animated Features
Angelica Pickles | Coco LaBouche | Jean-Claude | King Goobot | Ooblar | Poultra | Alphonse Perrier du von Scheck | Nick Vermicelli | Big Bob Pataki | Sloan Blackburn | Bree Blackburn | Siri | Sheldon Plankton | Mr. Krabs | Karen Plankton | Dennis | Cyclops | Victor | Dag | Nora Beady | Coyotes | Tortoise John | Rattlesnake Jake | Bad Bill | Hawk | Balthazar Douglas Peterson | Ivan Ivanovitch Sakharine | Allan | Tom | Pedro | Falcon | Aristides Silk | Red Rackham | Burger-Beard | Lasombra

Live-Action Movies
Marion Hawthorne | Kurt Bozwell | Troy and Griffin | Roxanne | Henry Gates | Count Olaf | Bald Man | Hook-Handed Man | White-Faced Women | Mulgarath | Red Cap | Goblins | Jake | Max | General Zhao | Fire Nation (Fire Lord Ozai, Zuko, & Azula) | Shredder | Foot Clan (Eric Sacks, Karai, Baxter Stockman & Bebop and Rocksteady) | Krang

           Spongebob Squarepants Villains

Main Antagonists
Plankton | Karen Plankton | Mr. Krabs | Mrs. Puff | Patrick Star

Recurring Antagonists
Flying Dutchman | Man Ray | Dirty Bubble | Bubble Bass

Movie Antagonists
Dennis | Victor | Cyclops | Burger-Beard

One-Time Antagonists
Every Villain Is Lemons | Kevin C. Cucumber | DoodleBob | Abrasive SpongeBob | Alaskan Bull Worm | Puffy Fluffy | Sergeant Sam Roderick | Tattletale Strangler | Lord Poltergeist | Carl | Big One | BlackJack SquarePants | Evil Alien Jellion Overlord | Sea Bear | Hash-Slinging Slasher | Flatts the Flounder | Con Man | Master Udon | Don Grouper | Gordon | Coupe | Abominable Snow Mollusk | Triton | The Fisherman | Madame Hagfish | Dead-Eye Plankton | Yeti Krab | Art Appraiser | Miss Gretel Puss | Planktonamor | Dreaded Patrick | Karen 2.0 | Dragon Jellyfish | The Jellions | SpongeBot SteelPants | Robot Plankton | ChefBob | Globulous Maximus