Don Grouper is the main antagonist of the SpongeBob SquarePants episode, "Goodbye, Krabby Patty?". He is a snowy grouper who works as an ad executive of Grouper, Goby & Koi, but in reality, he is a con artist seeking to become popular for his own selfish interests.
He was voiced by Jon Hamm.
According to Nickelodeon, he is "a charismatic head ad executive of the ad agency Grouper, Goby & Koi.
His "sharp mind and devastating charm make him an irresistible force. When Don's in the room, everyone laps up his words like overpriced organic honey," Nickelodeon says.
Don first appeared when Mr. Krabs showed him a "commercial" of Frozen Krabby Patties he made by himself. Don was not impressed by it, however, he tells Mr. Krabs that if he wants to be rich, he should keep his mouth shut and listen to him and the company. Afterwards, he introduced the staff of executives to Mr. Krabs and SpongeBob (whom he referred to as yellow box). Don showed Mr. Krabs various slogans on what the Frozen Krabby Patty should say on the box. SpongeBob came up with a slogan and says, "Krabby Patties: Tastes so nice that they taste nice". Don rejected it at first, but, he decided to have his star, Patrick use it for his commercial.
After the rehearsal, Don manipulated Mr. Krabs into changing the Krabby Patty formula so he can become rich faster, to which a gullible Mr. Krabs agreed to. Don gave SpongeBob and Mr. Krabs a tour to his factory. However, during the tour, SpongeBob discovers that his workers are suspiciously filling a filler with sand.
But Mr. Krabs tells them there's nothing to worry about for it was part of the process of making Frozen Krabby Patties. After Mr. Krabs got a check that holds a huge amount of money, Mr. Krabs turns the old Krusty Krab into a museum and his office is now a gift shop. Soon or later, Don, Mr. Krabs, and Patrick became so popular that everyone in Bikini Bottom kept buying more Frozen Krabby Patties, which completely disheartened SpongeBob. Eventually, SpongeBob learns that the Frozen Krabby Patties that Don had been manufacturing are made out of sand and decides to expose him for the fraud that he is. SpongeBob gives Patrick a freshly made Krabby Patty and their friendship has been restored. Later, at the shareholder's meeting, Don and Mr. Krabs allowed Patrick to speak to the audience before airing the 400th commercial.
Patrick begins his speech and with SpongeBob's guidance reveals to the audience that the frozen patties are made out of sand. The audience and Mr. Krabs are shocked at this sudden realization and learn that Don and his executives are frauds. With his secret exposed, Don walks off the stage while the audience vomits out sand. It is unknown what happened to him after the frozen patty factory was shutdown. However, it is assumed that he and his executives were arrested by the authorities after his fraudulent scheme was exposed.