Plankton

Sheldon J. Plankton is a fictional character and antagonist in Spongebob Squarepants. He is voiced by Doug Lawrence (often credited as "Mr. Lawrence").

Biography
Plankton is the nemesis and former best friend of Mr. Krabs. He is the owner of the Chum Bucket, a fast food restaurant located directly across the street from Krabs' restaurant, the Krusty Krab. The Chum Bucket primarily sells chum (bait consisting of fish parts), which is considered mostly inedible by the other characters. As a result, his restaurant is a commercial failure. Plankton's primary goal in the series is to steal the Krabby Patty Secret Formula so he can sell Krabby Patties at the Chum Bucket. 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".

A running gag throughout the series is the fact that Plankton is smaller than the other regular characters; he is easily stepped on and sent flying back to the Chum Bucket with a mere flick of the finger. His small size has led him to develop a Napoleon complex, which is occasionally manifested as a desire for global domination. He is a skillful inventor and regularly builds machines, both to help him in his plots, and for his own personal gain. Although he uses his intellect for evil, Plankton did not start out as a villainous scientist; he built Karen, his first invention and eventual wife, when he was friends with Mr. Krabs in grade school. Prominent in his earliest appearances, Plankton's catchphrase is "I went to college!". He also has a pet amoeba named Spot who at first was a guard dog, but later became a retriever.

Plankton's roles are not exclusively antagonistic. Outside of business, he seems to have a somewhat friendly relationship with SpongeBob. In The SpongeBob Movie: Sponge Out of Water, Plankton allies himself with SpongeBob, initially to protect himself from an angry mob, but gradually warms up to SpongeBob throughout the movie, even helping him retrieve the Krabby Patty secret recipe from Burger Beard. The movie has been described by The Guardian as a "buddy film" between Plankton and SpongeBob. Series creator Stephen Hillenburg considered Plankton to be "more of a caricature of a villain" than a truly evil character.