The protagonist. A positive, bright, and energetic sponge living in Bikini Bottom. He is yellow and square, both in body and pants. He makes Krabby Patties at the most popular fast-food joint under the sea, the Krusty Krab. He loves working there more than anything and gives 110% to both work and play! He loves his job so much he has won Employee of the Month 200 times. While pure and a bit clumsy, he is kind to everyone and cares deeply for his friends. He is emotionally unstable and will scream and run away normally when encountering danger. He is best friends with Patrick and Guest, and they always have fun together. He's a total goofball and an idiot. He thought he would become the manager of the Krusty Krab 2, but Mr. Krabs didn't give him the job because "he's just a kid," despite being the best fry cook under the sea. Like Patrick, he loves the mascot of the children's ice cream parlor "Goofy Goober"! He wants to be an adult and tries to act tough.

A fat pink starfish living in Bikini Bottom. He is lazy, easygoing, does things at his own pace, and is incredibly dim-witted. When in danger, he gets even more scared and runs away faster than SpongeBob. He often makes nonsensical comments. If called a kid, he gets offended and snaps, "I'm not a kid!" Sometimes, he happens to be useful in a pinch. He struggles with difficult concepts but has a kind heart and cares for his friends. He is best friends with SpongeBob and Guest. He doesn't work at the Krusty Krab, but he joins the adventure to recover the crown. Like SpongeBob, he is treated like a child.

A male octopus living in Bikini Bottom. He works as the cashier at the Krusty Krab. He is cynical, short-tempered, narcissistic, and always grumpy. He is fed up with SpongeBob and Patrick's noise and finds them a nuisance. He loves art and the clarinet, dreaming of the day his talent is recognized. He complains about everything but is somehow hard to hate. He is not cooperative regarding the adventure and doesn't come along (he said he was lucky to have the day off). He is the only one who notices Plankton's conspiracy and goes to confront him, but he is easily brainwashed by a Bucket Head hat. He speaks in a somewhat formal, grumpy manner.

A crab. The owner of the popular fast-food restaurant "The Krusty Krab" in Bikini Bottom. A cheap and greedy crab who loves money. He'll do reckless things for profit, but he values his employee SpongeBob. He highly regards SpongeBob's cooking skills and trusts him. He is frozen by King Neptune due to Plankton's conspiracy. Despite everything, he has a soft side.

The owner of the "Chum Bucket," the worst restaurant in the world, located in Bikini Bottom. Krabs' rival. A tiny green plankton about the size of a foot, obsessed with stealing the Krabby Patty secret recipe. He is very intelligent (yet a total moron) and a cunning strategist, but his plans usually fail. This time, he executes "Plan Z," causing a major incident by stealing King Neptune's crown. Using the stolen recipe, he starts selling Krabby Patties at the Chum Bucket. He distributes hats (which brainwash anyone wearing them at the push of a button) to customers, brainwashing them into building statues of him and turning Bikini Bottom into "Planktonopolis."

The majestic King of the Sea who rules the ocean kingdom. Characterized by his large crown, he possesses powerful magical abilities. He is prideful, arrogant, short-tempered, and quick to anger. He orders executions instantly. He cherishes his daughter Mindy, but he is bald and very self-conscious about his hair. Because his baldness would be exposed, he is furious that his crown was stolen and assumes Mr. Krabs is the culprit. He is so focused on trying to grow hair that he doesn't notice Plankton conquering Bikini Bottom.

King Neptune's daughter. Princess of the sea kingdom. Unlike her father, she is kind, gentle, and compassionate. She is understanding of humans and sea creatures alike, and she warmly watches over SpongeBob, Patrick, and Guest. She cheers on the trio as they set out to recover the crown and is a reliable ally who helps them during their adventure.

Plankton's wife. A high-performance computer developed by Plankton. She is calm, composed, highly intelligent, and skilled at cynical remarks and sharp retorts. While she sometimes helps with Plankton's evil schemes, she is often exasperated by his reckless plans. She is fundamentally smarter than Plankton, and their bickering is a highlight. This time, she doesn't seem very interested.