They began as minor characters, but Lawrence developed their personalities throughout the show's early seasons and they eventually became the franchise's main antagonists.

The Planktons play central roles in The SpongeBob SquarePants Movie, which promoted them both to main cast members in its credits, and in the 2015 film.

His villainous efforts to do this are widely known within the show; fellow character Squidward Tentacles refers to Plankton as "the most hated thing in Bikini Bottom".

Although he uses his intellect for evil, Plankton did not start out as a villainous scientist; he built Karen, his first invention, when he was friends with Mr. Krabs in grade school.

Fellow voice actor Tom Kenny found it amusing, leading to Lawrence's decision to use it when auditioning for roles on SpongeBob.

[6] Lawrence initially tried out for the role of SpongeBob during the series' pre-production, but Stephen Hillenburg wanted a more innocent voice for the character and turned him down.

In his review of the fourth season, Paul Mavis of DVD Talk stated that adult viewers would likely find Plankton more amusing than others, praising his "hilariously stentorian" voice.

[21] In his review of the season six episode "Clash of Triton," Mavis called Plankton "the only secondary SpongeBob character who can [successfully] anchor his own short".

[22] Bettijane Levine of The Los Angeles Times wrote positively of Plankton's portrayal, calling it poignant rather than genuinely immoral, describing him as a "town meanie... but mean is different than evil.

"[23] Ann Hagman Cardinal of Blogcritics praised the character, rhetorically asking in a 2007 review, "who isn't tickled by the tight-jawed, Kirk Douglas-voiced Plankton with his silent moviesque evil plans to steal the secret recipe for the Krabby Patty?

He noted that "no one thinks it's strange that the town villain, the megalomaniacal Plankton, is a one-celled organism" as part of the "colorful, goofy" atmosphere of the program.

[27] In 2015, Entertainment Weekly's Hillary Busis named Plankton one of the most devious characters on television, adding in her commentary that he is "voiced to wicked perfection by Doug Lawrence".

[28] José Antonio Gómez Marín of El Mundo favorably compared Plankton's plans to the stories of Georges Simenon in a 2013 article.

[33] Karen takes on various jobs at the Chum Bucket, including busser, chef and cashier; she rarely has to fulfill them because of the restaurant's unpopularity.

Tom Kenny addressed this in a 2004 interview with the Associated Press, stating that Karen's functionality is a "don't-ask-why" aspect of SpongeBob and that "logic doesn't have a place" in the series' universe.

[5] Hillenburg initially designed a laboratory for Plankton to convey the character's technological abilities, leading to Karen's development as his lab's central computer system.

The married life of an evil genius is the funniest thing to me, so in that regard [Karen] definitely enhances Plankton's stories, making him more than just your typical bad guy.

"[41] For the first three seasons, Karen was usually depicted as a large, blue monitor in the Chum Bucket's laboratory;[42] at other times, only her voice is heard from within Plankton's robotic creations.

In a 2010 review of SpongeBob's Last Stand, DVD Talk's Paul Mavis wrote highly of Karen and Plankton's dialogue, stating that the two "could have their own sitcom".

[49] Sandie Angulo Chen of Common Sense Media praised the amount of screen time given to Karen in Sponge Out of Water, calling her "hilarious".

[51] The About Group's Nancy Basile commended Jill Talley's portrayal of the character, saying that it is "no surprise she plays [the role] so well" due to her earlier work with Second City and Mr.

[47] In an analysis of how the show has changed throughout its run, Channel Frederator argued that the main characters of SpongeBob–specifically Sandy, Patrick, Mr. Krabs, Squidward and Karen–have been reduced from multidimensional to reliant on single traits.

He considers this trope one of several harmful stereotypes present on the program, writing that "the motif of the nagging wife is certainly an issue worthy of dissection in dealing with a young audience, along with the spoiled teen daughter [Pearl] and the stupid best friend [Patrick]".

[40] Lampooning a controversy surrounding SpongeBob's sexuality, essayist Dennis Hans wrote a 2005 satirical piece for the National Catholic Reporter focusing on the marriage of Plankton and Karen.

[62] Additionally, Plankton and Karen are both mentioned by Eric Lange (as his character Sikowitz) in "Tori Goes Platinum," an episode of Nickelodeon's sitcom Victorious.

[63] Sea World Australia's "SpongeBob ParadePants" event, which opened in December 2011, included a float featuring Karen and a talking Plankton.

[64] In 2015, a recreation of Plankton's laboratory was constructed for a SpongeBob event at the Chiang Kai-shek Memorial Hall in Zhongzheng District, Taipei.

[67][68] Plankton sings a track on the novelty album The Best Day Ever titled "You Will Obey," on which Elvis Presley's former guitarist James Burton played guitar.

[69] Of the album, Tom Kenny said "one of our hidden Easter eggs that hopefully more than three people in the world will get is during the guitar solo when Plankton says 'Take it, James', which was what Elvis said in every one of those concert movies".

[74] In addition to wearing costumes inspired by the characters, Taylor and Hsu are accompanied by a Plankton puppet and a replica of Karen's mobile form, respectively.