Karen's system is built into most of Plankton's inventions. She has two main forms: a big monitor on the wall of the Chum Bucket and a portable wheeled computer. Along with her role as co-owner of the Chum Bucket, she works as the busser, chef and cashier. She rarely has to fulfill these jobs due to the restaurant's unpopularity.
As revealed in "Friend or Foe," Plankton originally installed Karen as a security system at the Dump. It is implied in "Goo Goo Gas" that Karen was a calculator as a baby. He has also referenced using "a jumbled mass of diodes and wires" to turn her into a large computer. It has been stated on multiple occasions that Plankton built Karen entirely by himself. She does, however, have parents.
Plankton and Karen dated while Plankton was still in school. It was the day of their third date when Mr. Krabs and Plankton became enemies. When he and Karen got married, Plankton had a head full of hair and a bushy mustache.
A photograph of them at their wedding can be seen in "Komputer Overload." Despite how they are both happy in the picture, Karen states that she "never agreed" to be with Plankton in The SpongeBob SquarePants Movie. Karen has all of her old memories with Plankton stored in her databanks.
Karen and Plankton have lived in the Chum Bucket throughout the entire series. Karen's system is built into many parts of the building, such as the metal fist on top of it. It is shown in "Plankton's Good Eye" that Karen has control of the Chum Bucket's light fixtures. It is implied in "Krabby Road" that the Chum Bucket belongs to Karen more than it does to Plankton, because she kicks him and his few belongings out of the house in the episode.
Karen does not have a heart, as stated in a conversation between her and SpongeBob in "Friend or Foe." However, this does not prevent Karen from expressing emotions or feeling true love for Plankton. She does not often show it, but Karen cares for Plankton more than anything else; almost everything she does revolves around helping him in some way.
Karen loves Plankton for his evilness. This is best seen in "Plankton's Good Eye," in which she is appalled when Plankton starts to inadvertently abandon his evil ways after growing a second eyeball.
According to Plankton, Karen likes to take long walks on the beach, and talk about their dreams of conquering all of Bikini Bottom.
Plankton needs Karen much more than she needs him. Without her, Plankton is unable to come up with feasible schemes and forgets how to complete basic tasks like blinking, as seen in "Komputer Overload." He has left and replaced Karen multiple times throughout the show but always ends up coming back to her and admitting that he is nothing without her.
In the SpongeBob SquarePants musical, Plankton and Karen are a duo who are bent on dominating the world together. Unlike in the show, Karen wants world domination just as much as Plankton.
Karen's wall form is a large, dark blue monitor with a black screen. Her neon green facial features, usually a waving line, are projected on the screen. To the left of the screen is a silver keyboard with an oval-shaped green button on the top and nine pink keys on the bottom. There are three silver tubes on the right side. There is a silver control panel connected to the bottom of her screen. Although its appearance tends to change, it usually has a red lever, a circular analog clock, a green keypad, and several multicolored buttons on it.
Karen's mobile form contains a light blue head in the shape of a desktop computer, a black screen, a silver stand, and a silver base with wheels. From seasons 4 to 9, there are two red keys on the base. From the second half of the ninth season onward, the keys are aqua-colored.
In The SpongeBob SquarePants Movie, Karen's mobile form is much different from her standard one. It is much taller and made of dark silver metal. Her wheels appear to be completely disconnected from her base, which is shaped like a square. Her screen is dark blue instead of black.
Karen's system has several forms of manifestation aside from her monitor and mobile computer, listed below:
Chum Bucket fist - In "20,000 Patties Under the Sea," it is shown that Karen's system is built into the metal fist situated at the top of the Chum Bucket. It is able to become an independent vehicle, and Plankton uses it as a traveling restaurant in the episode. Karen is heard speaking from the inside.
Brain control: Karen is able to activate the Bikini Bottomites' brain-control devices in The SpongeBob SquarePants Movie.
Karen and Plankton share a family. In "Dunces and Dragons," it is shown that Karen has a medieval ancestor named Karen the Crystal Ball who resembles her and shares her first name. The episode implies that the Plankton family has included marriages between plankton and pieces of technology for generations.
Karen's parents have been shown. Her mother, E.M.I.L.P., disapproves of her choice to marry Plankton and thinks she should have married an ATM. Her father, Fredrick, has not made an appearance on the show; however, he can be seen in an issue of Nickelodeon Magazine. He is reportedly an old-fashioned desktop computer.
Karen was first introduced as Plankton's computer system who would be a part of all of his inventions. She was named after Karen Hillenburg, the wife of the series creator Stephen Hillenburg. Her voice is provided by Jill Talley, who is the wife of SpongeBob's voice actor, Tom Kenny.
Karen's first appearance in "Plankton!" does not reveal much of her personality, since she is used as a part of Plankton's analyzer and does not have a conversation with him. Her role is expanded upon in "F.U.N.," which shows that she is sentient and supports Plankton on his mission to retrieve a Krabby Patty. Her appearances throughout the second season establish her as a key part of Plankton's plans. "The Algae's Always Greener" is the first episode that explicitly defines her as Plankton's wife.
In the first season of the show, when cel animation was used, the animators used a green light behind Karen to create a glowing effect on her screen. Whenever she appeared in a storyboard, the artists would write the note "Back Lit Line" to let the animators know when to use the lighting effect.
In The SpongeBob SquarePants Movie, a mobile form of Karen debuted. In later episodes, she is able to switch between her wall and mobile forms. However, her mobile form in the episodes is noticeably smaller and has a lighter color scheme. Since the first movie is intended to take place at the end of the series' timeline, Karen's taller and darker-colored mobile form from the 2004 movie is actually her final version.
Sheldon J. Plankton
Plankton and Karen love each other very much, but they do not always like to admit it.
In The SpongeBob Movie: Sponge Out of Water, Plankton tries to tell Karen how much she means to him. After Karen says that powering the time machine will take all of her energy, Plankton takes a moment and says, "Well, Karen. I know I've taken you for granted all these years and I... I just wanted to say... I'm glad you're on my tee-am." He starts to listen to Karen respond; she says "Oh, Sheldon, that's the sweetest thing you've ever s--" but Plankton is so caught up in his emotions that he cannot bear to hear her finish the sentence. He starts to cry in front of SpongeBob.
Karen tends to come up with possible ideas to steal the formula, much more so than Plankton. In "F.U.N.", "Welcome to the Chum Bucket," "The Algae's Always Greener," and "Chum Caverns," she gives Plankton ideas that he uses are his. A reappearing theme of their relationship is that Karen will come up with an idea, but Plankton will take the credit for it.
"Plankton's Army" reveals that Plankton had never told Karen his embarrassing first name, Sheldon, until that point. The SpongeBob SquarePants Movie shows that Plankton considers Plan Z the second greatest thing to happen to him, the first being Karen agreeing to marry him. Karen then, likely joking, remarks that she never agreed to marry Plankton.
Numerous episodes feature Karen supporting Plankton's evil ways. In the first three seasons, she is almost always very positive and genuinely cares about his plans. A good example of this in a later episode is "Truth or Square," where Plankton complains that he is a failure but Karen encourages him to get the formula. She tells him that the Krusty Krew will be busy with their anniversary party and not notice.
"Enemy In-Law" is the first episode to show Karen's jealous side and the first to reveal that Plankton can be disloyal to his wife. Karen gets offended and jealous when Plankton falls in love with Mama Krabs. "Mermaid Man vs. SpongeBob" includes a reverse of this situation; in the episode, Plankton thinks that Karen is cheating on him with Mr. Krabs because he sees them laughing together.
"Krabs à la Mode" is a later episode in which Karen gives Plankton an idea. This episode also features Plankton being sarcastic towards his wife and Karen asking herself why she encourages him. This episode is the first to portray their relationship as one similar to that of an old married couple. Similar tropes are used in following episodes.
In "Plankton's Regular," Karen secretly pays a citizen named Nat Peterson to eat at the Chum Bucket. She does this to make Plankton happy so that he does not complain about his life any longer. Plankton finally finds out when Nat returns the money Karen gave him.
In "Chum Bucket Supreme," Plankton asks her what napkins they should use. This means that he genuinely cares about her opinions.
Many episodes show that Karen is even smarter than her husband, who is a well-educated genius. One such instance is "Banned in Bikini Bottom," in which Plankton thinks that the Krusty Krab has changed its name to "Closed" and Karen tells Plankton that Miss Gristlepuss actually shut the place down.
"Komputer Overload" shows the upsides and the downsides of the couple's relationship. Karen leaves Plankton after feeling mistreated. She argues that Plankton is dependent on her and he claims that he does not need her to get the formula. He then builds three robots to replace her. He causes destruction around town with the robots. He is about to get the formula when the robots turn off unexpectedly. Karen returns to get her keyboard and Plankton admits that she was right. They hug and go home after making up to each other.
"Single Cell Anniversary" is one of the best episodes in regards to Plankton and Karen's relationship. In the episode, it is their anniversary and Karen obtains a copy of the Krabby Patty formula as a gift to Plankton. At first, Plankton just wants to give her something so that he can get the formula, but he eventually gives her a gift from the heart. He enlists the help of SpongeBob and Patrick to write and sing a love song for Karen. She loves it and cries tears of joy.
In "Walking the Plankton," Plankton gets tickets to a cruise ship for Karen and Plankton's second honeymoon. Karen points out that they never had a first honeymoon. She is very excited and happy, later remarking that Plankton is so sweet when he is not obsessing over the Krabby Patty formula. However, she later finds out that it was all a plot to retrieve the recipe and is mad at Plankton.
In "Karen 2.0," Plankton builds a new wife to replace Karen because she is getting old. Plankton kicks Karen out and she starts working at the Krusty Krab. Eventually, Karen's replacement (Karen 2) fights with Karen over Plankton. In the end, Karen 2 rolls over Plankton and hurts him. Although Karen is at first mad at Plankton, she is devastated when she sees him injured. This causes her to destroy Karen 2 and protect Plankton. However, her battery drains. Plankton saves her by taking the battery from Karen 2 and replacing Karen's old battery with it. Karen wakes up and thinks that her replacement was all part of a dream. Plankton plays along as they happily go back to the Chum Bucket.
"Jailbreak!" shows a very loving and compassionate side of Karen. Plankton is in prison and Karen visits him with a cake that she baked. He asks why there is no file in it like he requested and Karen wonders why he would want a file in a cake. She does not realize it is part of his escape plan.
In "Plankton's Pet," Karen suggests that Plankton should get a hobby to keep himself happy. Plankton is not sure what to do, so Karen recommends a pet. This ends up being a very good fit for him.
In "Plankton Gets the Boot," when Plankton insults Karen's new screen saver Karen becomes filled with rage and kick Plankton out of the Chum Bucket as well as shutting doors completely to him.
Overall, their relationship has had its ups and downs, but they both love each other and have just been married so long that they tend to bicker.
Because she is on Plankton's side, Karen sees SpongeBob as a pawn for retrieving the secret formula. This is first shown in "F.U.N." when Karen tells Plankton that he should befriend SpongeBob in order to get the recipe. However, Karen knows that SpongeBob can potentially be an actual threat to Plankton's plans. In The SpongeBob SquarePants Movie, Karen warns Plankton that SpongeBob and Patrick could expose him for the fraud that he is. This eventually happens at the end of the film, just like Karen said.
In "Plankton's Regular," SpongeBob disguises himself as Karen in an attempt to fool Nat Peterson into eating a Krabby Patty. He throws Karen into the Chum Bucket's backroom and tapes her up. He then morphs into the shape of Karen's mobile form and pretends to make "bleep blap" sounds to sell the disguise.
Karen and SpongeBob do not hate each other. In "Single Cell Anniversary," SpongeBob helps Plankton write a song for his anniversary with Karen. In "Frozen Face-Off," SpongeBob is shown to care for Karen. He spots something freezing in the snow and remarks, "it looks like...Karen!" He and Sandy decide to save her by breaking her out of the ice.
In "Friend or Foe," she reveals Mr. Krabs and Plankton's story to SpongeBob and the customers of the Krusty Krab. This shows that she somewhat trusts SpongeBob. In "Perfect Chemistry," Karen does not seem to detest working with SpongeBob.
In "Bucket Sweet Bucket," both SpongeBob and Patrick are shown to care for Karen. Plankton persuades them into remodeling the Chum Bucket by telling them that Karen really wants it. He says, "I need your artistic vision. You, wouldn't want to disappoint my Karen, now would you?" They respond, "No, sir. Uh-uh!"
In "Jailbreak!," SpongeBob is nice to Karen and greets her when she visits Plankton in jail. He says, "Hi, Karen! Look, Plankton, Karen came to visit! And she brought you a cake." He then allows Plankton and Karen to have some time alone.
The SpongeBob Movie: Sponge Out of Water is an example of Karen and SpongeBob working together to achieve a common goal. In the movie, SpongeBob and Plankton save Karen from a dungeon. She then helps the two, who are outlaws because they are blamed for stealing the formula and the citizens think that SpongeBob has betrayed Mr. Krabs. Karen becomes a time machine that eventually allows them to save the day.
"Plankton's Good Eye" shows that Karen dislikes cheery people like SpongeBob. She dislikes Plankton's new eye, which was given to him by the DNA of SpongeBob and caused him to act nice.
Karen and Patrick generally do not interact. However, Patrick does not seem to realize that Karen is evil. He tries to help Plankton make Karen happy in the episodes "Bucket Sweet Bucket" and "Single Cell Anniversary," showing that he does not dislike her.
Squidward does not care very much about Karen or Plankton. One exception is The SpongeBob SquarePants Movie, in which Squidward is attacked by Plankton's slaves after Karen activates their helmet brain-control devices. Another is "Bucket Sweet Bucket," in which Squidward builds a desktop computer for the redesigned Krusty Krab out of Karen. A third is "Chum Fricassee," in which Squidward teams up with Plankton and Karen to start his own restaurant. Karen works as the waitress. Overall, Karen and Squidward have a neutral relationship.
Eugene H. Krabs
Much like Karen and SpongeBob's relationship, Karen and Mr. Krabs' relationship is generally a negative one because they are enemies. "Best Frenemies," "Mermaid Man vs. SpongeBob," "Frozen Face-Off," and "Karen 2.0" are the only episodes in which the two are not against each other.
In "Best Frenemies," Karen tries to tell Mr. Krabs and Plankton what the Kelp Shakes are made of. Unfortunately, they do not listen to her and end up drinking the shakes, which cause them to become furry monsters.
In "Mermaid Man vs. SpongeBob," Karen asks Mr. Krabs for two Kiddie Meal toys to give to Plankton. When she brings a meal to Plankton, he asks her, "What's that? A souvenir from your boyfriend Krabs?!"
In "Frozen Face-Off," Karen and Mr. Krabs work together to survive after both almost freeze to death, only to be saved by SpongeBob and his friends.
In "Karen 2.0," Plankton builds a replacement Karen and he kicks her out. Mr. Krabs and SpongeBob find her on the curb and take her into the Krusty Krab. When she boots up, she tells the two about her worries. Unexpectedly, Mr. Krabs sympathizes with her and gives her a job. When Karen 2 and Plankton show up to steal the formula, Karen and Karen 2 start fighting and Mr. Krabs takes the opportunity to have customers place bets on who will win.
In "Lame and Fortune," Mr. Krabs thinks about what his funeral would look like. It is shown that Karen would attend alongside Pearl and his other relatives, implying that she does slightly care about him.
Unlike her other relationships, Karen's relationship with Sandy is a purely positive one. They are both level-headed and intelligent characters with an appreciation for inventions, which is why they have had friendly interactions throughout the series.
In "Perfect Chemistry," the two meet and Sandy calls Karen beautiful. Karen is very happy about the compliment.
In "Frozen Face-Off," Sandy and friends save Karen from being frozen. Later, Sandy uses Karen's body to save Squidward, who has been frozen in a block of ice.
In "Salsa Imbecilicus," Karen and Sandy are the only residents of Bikini Bottom who were not turned into idiots by the steam from Plankton's sauce. They work together to create a university, which eventually returns everyone else to their normal intelligence. This episode reveals that Karen knows where Sandy lives and that her home is called a treedome, implying that she has visited Sandy.
In "Girls' Night Out," the two and Mrs. Puff spend a night out together, and the three refer to one another as "Gal Pals" throughout the episode.
Gary the Snail
Karen does not mind Gary. Karen is neutral about Plankton's plan to impersonate Gary in "Shellback Shenanigans." At the end of "Frozen Face-Off," Karen lets Gary sit on top of her. Gary stays on top of Karen until Plankton tries to fry them in a vat of boiling oil.
Karen does not like Pearl and does not care about her very much, either. In "The Algae's Always Greener," Plankton tells Karen that Pearl is "as big as a whale," not realizing that she is actually a sperm whale. Karen dismisses this comment and seems to understand Pearl's species better than her husband. In "One Coarse Meal," Plankton becomes very afraid of Pearl after Mr. Krabs starts to dress up as her and frighten him. Karen does not take Plankton's temporary phobia of Pearl seriously and seems to think he is crazy. This shows that she is not afraid of Pearl.
The only time the two have actually interacted is in "Patnocchio," where Karen - as the Computer Fairy - gives Pearl a bottle of Gush and Flush to ease her stomach pain, which Pearl thereby consumes and thanks Karen for.
Karen appears in many SpongeBob SquarePants video games and mobile apps.
Creature from the Krusty Krab - At the beginning of the level "Revenge of the Giant Plankton Monster," Karen accidentally wakes up the sentient patty by saying "good morning" to Plankton. She then turns Plankton into a supersized monster.
In the comic "Krusty Karen," it is shown that Karen can change the color of her screen depending on her mood. It is blue when she is sad and red when she is angry.
In several episodes, Karen appears in her mobile form with an extension cord. She is wireless in most of her other mobile appearances.
Plankton once referred to Karen as an electroencephalograph. An electroencephalograph is a monitor that measures electrical activity in the brain.
In "All That Glitters," a monitor that looks exactly like Karen in her portable form is seen in the hospital. In "Shellback Shenanigans," Plankton mistakes it for Karen.
In "Not Normal," SpongeBob says that he needs to defragment his computer's hard drive. Karen also says that she does this.
When SpongeBob puts tape on Karen's screen in "Plankton's Regular," her speech is muffled. This implies that her screen acts as a mouth.
Similarly, in "Shellback Shenanigans," Karen is unable to see what SpongeBob and Mr. Krabs are saying without a telescope. This implies that her vision is similar to that of a character with real eyes.
The fist on the Chum Bucket is very similar in appearance to Karen's hands.
In "Single Cell Anniversary," Karen has a slot on the side of her screen that scans food. She also has this feature in the app SpongeBob's Game Frenzy.
Many pieces of merchandise unrelated to the first movie use Karen's design from that film.
In "Plankton Gets the Boot," Karen's wall form is seen in the background with a very different appearance. The monitor is thinner than usual with a dark blue keyboard and red/white buttons, instead of a silver keyboard and light red buttons.