He is the main antagonist of The SpongeBob SquarePants Movie, the anti-heroic deuteragonist of The SpongeBob Movie: Sponge Out of Water, and the secondary antagonist, later supporting protagonist of The SpongeBob Movie: Sponge on the Run.
The SpongeBob Movie: Sponge Out Of Water
While in the middle of yet another scheme to steal the Krabby Patty secret formula, the formula unexpectedly vanishes after Burger-Beard writes on the magical book he found. After Mr. Krabs and numerous citizens of Bikini Bottom were accusing and berating at Plankton for being the culprit, SpongeBob convincing to them that he's innocent rescues him with a giant traveling bubble as they escape the hostile people who suddenly formed a group of apocalyptic sufferers.
As SpongeBob and Plankton watch Bikini Bottom become an apocalyptic wasteland, SpongeBob tries to get Plankton to become his teammate, which Plankton was reluctant with joining SpongeBob's side pronouncing "teammate" as "tee-am-mate". SpongeBob tries to get Plankton to understand the meaning of teamwork, which Plankton barely understands. After trying to find the secret formula in SpongeBob's brain that's literally full of kindness and sweetness, Plankton and SpongeBob decide to time travel to get back the secret formula. So they sneak into the Chum Bucket to rescue Karen who was imprisoned by the savage people, and use her as a power source for a time machine made out of parts from an abandoned taco restaurant, then they go to the future where they meet Bubbles who has a job to look after the cosmos. Then when SpongeBob and Plankton mistakenly made Jupiter and Saturn crash into each other, Bubbles finds out and starts shooting at them because what they've done could make him lose his job. SpongeBob and Plankton escape and try to go to the past where they see Bikini Bottom a few days in the future in a desert like state where a bearded future Patrick told them that everyone given up on finding the Krabby Patty secret formula. Then while they go right to the past day when the secret formula disappeared, Plankton distracts their past selves as SpongeBob takes back the secret formula.
On the way back to the present, Plankton started to get used to teaming up with SpongeBob. However, when they got home and showed the formula to everyone which turned out to be a fake one that Past Plankton was replacing the formula with with an "in your face" note for Mr. Krabs. This angers the savage people even more, as Plankton angrily accuses SpongeBob for making that foolish mistake of taking the wrong formula. An upset SpongeBob argued that they're supposed to be teammates, and that it's selfish to take something like secret formula to yourself. After the town threatened to sacrifice SpongeBob since Sandy believed it could be a gift to the "burger gods", SpongeBob then tells everyone that he smelled a familiar scent coming from far away, and when they finally smelled it also, SpongeBob gets Patrick, Squidward, Sandy, and Mr. Krabs right up the where the scent is coming from. Plankton secretly joins in hiding in SpongeBob's sock. Bubbles returns and thanks SpongeBob for having him be free from his job and offers SpongeBob and his friends the ability to survive above the surface, and launches them up to the beach. As they face Burger-Beard, who's the culprit of stealing the secret formula to open up his new restaurant, he uses the magic book to banish them to Pelican Island to be devoured by the pelicans there. While there, SpongeBob was fortunate enough to find a page from the magic book and uses a pelican feather and Squidward's ink to write them back to fight Burger-Beard as superhero counterparts (SpongeBob as the Invincibubble, Patrick as Mr. Super-Awesomeness, Squidward as Sour-Note, Mr. Krabs as Sir Pinch-a-Lot, and Sandy as the Rodent). Little did they know Plankton sneaks in to write something as well in.
While fighting against Burger-Beard, Plankton, as the giant muscular Plank-Ton, surprising comes to rescue SpongeBob and friends and defeat Burger-Beard, revealing that he also wrote for himself to become a superhero and to rescue SpongeBob from Burger-Beard. Then Plankton knocks Burger-Beard straight to the island above Bikini Bottom. Then as Plankton gets a hold of the secret formula, instead of taking it for himself, he decides to give it back to Mr. Krabs and thanks SpongeBob for teaching him about teamwork, and how selfish it is to keeps things to himself, and offers SpongeBob the remaining page to take them back home and set things back to normal. Then as the Krusty Krab goes back in business with Krabby Patties returning to Bikini Bottom, Plankton then decides to go back to his role as the business rival of the Krusty Krab back to his formula-stealing schemes just to keep things the way they normally were before. As SpongeBob catches him he uses Gary to scare him away, and then he waves goodbye to him saying, "See you later, 'tee-am-mate'!"
Plankton is evil, intelligent, charismatic, ironic, and funny.
He sometimes has a heroic side and he shows up it when he teams up with his former enemies and rivals (though he still continues to steal the formula).
- In The SpongeBob Movie: Sponge Out of Water, he teamed up with SpongeBob to save Bikini Bottom, and rescue Karen from being imprisoned by savage people. He also gave the Krabby Patty formula back to Mr. Krabs after Burger Beard stole it with a magic book, and then he helped defeat Burger Beard. He was also one of the superheroes in the film. This was perhaps his most heroic act.
- In a short called Can't Swim, Plankton saved Mr. Krabs from drowning.
- In Plankton's Good Eye, he attempted to save Bubble Bass from a burning building, although Bubble Bass was able to help himself escape. He also returned the Krabby Patty Formula to Mr. Krabs like a nice person.
- In Karen's Virus, he helps SpongeBob to save Karen by removing a virus from her, and tells SpongeBob that he really needs to save Karen.
- In Plankton's Pet, when Plankton lost his pet named Spot, he teamed up with SpongeBob to find him and prevent him from being lost again.
- In Karen 2.0, Plankton saves Karen by replacing her old battery and replace it by taking the battery from Karen 2.
- In The Krusty Bucket, Plankton and Mr. Krabs joined forces to try and stop Plankrab after he merged the Krusty Krab and the Chum Bucket into one restaurant.
- In Single Cell Anniversary, he teamed with Spongebob to find Karen a good anniversary gift. Though, it was partly a trick to get the formula.
- He does sometimes have remorse for his actions.
- While Plankton was a true villain in the older seasons and he was pretty evil in some other episodes afterwards, in the newer episodes Plankton has become a stereotypical villain like Heinz Doofenshmirtz from Phineas and Ferb. Just like him Plankton is shown to be sympathetic, actually cares about people and helps often the protagonists of the show when they are in trouble.
- Plankton found Mr. Krabs' life to be worse than his own when he experienced it in "The Algae's Always Greener" and "Spy Buddies". In "The Algae's Always Greener", he found lots of reasons that make Mr. Krabs' life difficult:
- SpongeBob is always asking him for a Weekly Performance Review on Tuesday and throws a temper tantrum if Plankton refuses. He also keeps yelling "SOILED IT! SOILED IT! SOILED IT!" when he accidentally gave a customer a large soda when the customer wanted a medium soda.
- Squidward, the lazy, grumpy, pessimistic worker at the restaurant, complains to Plankton that he doesn't want to work with SpongeBob. Later, when Plankton put him in charge of fry cooking, a customer got angry because the Krabby Patty that Squidward cooked was very ugly, disgusting-looking, and hideous.
- Pearl, his virtual reality daughter, throws a big temper tantrum because she doesn't get more than $1 advance to her allowance.
- Krabs tries to steal the Krabby Patty formula (which Plankton actually does in the show's reality), and Krabs NEVER gives up like he does. This version of Krabs, well not as smart as Plankton, is even more unhinged in his attempts.
- In The SpongeBob SquarePants Movie, Plankton was a lot more evil and depraved than he was in the series as he was ultimately grown into an alarmingly dangerous threat to the entire ocean. In the said movie, he stole King Neptune's crown, frames Mr. Krabs for it, sends Dennis to kill SpongeBob and Patrick rather than merely get rid of them, enslaves Bikini Bottom (which also includes not allowing his slaves to earn a single rest or break and just work nonstop) and shows excitement and joy when Mr. Krabs is going to be killed (in spite of their former friendship, yet his past relationship with Krabs had yet to be established when the movie came out). He also enslaved King Neptune, in which gave him a potentially powerful asset in conquering the whole ocean and the world. And that was the only time he acted exactly pure evil so that means that was by far the worst thing he has ever done.
- However, it is revealed that Burger-Beard had previously surpassed Plankton (if one count the second movie as prequel to first film) as aside managed to instantly steal the Krabby Patty recipe simply by rewriting the magic book that records everything that occurs in the ocean (especially events in Bikini Bottom includes conflict between Plankton and Krabs), the pirate was able to destroy Bikini Bottom and render it into post-apocalypse state in an instant. Even in order to defeat Burger Beard, it took the superpowered SpongeBob, Sandy, Patrick, Krabs, Squidward, and Plankton himself to defeat him.
- Early in the series, Plankton is considered a true villain. Later, as Krabs becomes more dramatically greedy (said greed ultimately drove him insane) and Plankton becomes less dramatically evil and less of a genius, the role of the main villain of the series becomes more debatable as lots of people think that Mr. Krabs is evil. Plankton also acknowledges this himself when he begins to question whether he or Krabs is truly evil.