Mrs. Puff
Mrs. Puff is very paranoid, mean and erratic, and has had a history of mental instability.It is implied that she has had to move to another town and start a new life with a new name in the past. While this is mostly caused by SpongeBob's antics, it is possible that some of it is caused by loneliness she suffers from after her husband was killed by humans and made into a lamp.At the beginning of the series, Mrs. Puff is more friendly to SpongeBob and actually treats him like a close friend, save for a few moments when SpongeBob crashes during the course. However, as the series has progressed, Mrs. Puff seems to have developed an intense hatred for him, and can even get a fit of mental instability by just looking at him. This could be because of the fact that SpongeBob becomes more troublesome as the series progresses, and has caused Mrs. Puff great trouble lately.
Pearl Krabs
Pearl Krabs is the daughter of Eugene Krabs. She is a whale, which means Mr. Krabs was once married, and her mother was a whale. She is a cheerleader too.Pearl is a teenage girl who interested in anything a normal teenage girl would be interested in. She sometimes acts like a crybaby to Mr. Krabs. She also gets angry easily when annoyed. She will cry when she dosen't get what she wants.
Karen Plankton
Karen Plankton is Plankton's wife, a Mark II UNIVAC. She is the main computer system of Plankton's lab, and is often the source of his plots (even though Plankton takes all the credit). Karen usually manifests on the large-screen computer in Plankton's lab, but sometimes acts through a portable wheeled computer. The two frequently argue, and Karen is often very bossy, sarcastic, and cynical to her husband, having nagging software installed in her. She also thinks Plankton's first name, Sheldon, is funny which is why Plankton had to unplug her after she kept making fun of his name, Sheldon, even when he told her to stop. Karen is often indifferent to her husband's plots to defeat Mr. Krabs and often shows very half-hearted dedication to his plans for domination over others. Despite their differences, Plankton has said that marrying Karen was the greatest thing that ever happened to him. Unlike Plankton, however, Karen shows some degree of dedication for her husband. This is evident whenever she appears, often showing it in the form of assistance in Plankton's schemes, consoling him whenever he's down, and even crying upon Plankton when he told her what W.I.F.E. stands for. It is most likely that Plankton either ignores, or cannot register the acts of kindness that Karen often performs for him, resulting in their various feuds.
Larry the Lobster
A bodybuilder lobster who always works as a lifeguard at Goo Lagoon or just working out at a gym.
Flying Dutchman
The Flying Dutchman is the main ghost in Bikini Bottom. His main job is scaring the residents of Bikini Bottom and making them believe in ghosts. The Flying Dutchman may prehaps be friends with SpongeBob due to SpongeBob letting him stay at his house on more then one occasion.The Flying Dutchmans body used as display as a display in a Gift Shop when he died and that's why he haunts the seven seas because he was never put to rest. It is also revealed that The Flying Dutchman has been the knot champion for the last 5000 years.
Marmaid Man
Mermaid Man is a underwater superhero who lives at Shady Shoals Rest Home with his sidekick Barnacle Boy. In present day,he is depicted as an old and sometimes senile man. Many of his main enemys include Man Ray, the Dirty Bubble and many more. Mermaid Man is SpongeBobs favorite superhero with SpongeBob almost always chasing for an autograph.Mermaids feelings to SpongeBob vary Mermaid Man is eager to run away from Spongeabob he is nice to SpongeBob or he can be quite mean.
Barnacle Boy
Barnacle Boy, along with Mermaid Man is a semi-retired superhero that lives at Shady Shoals Rest Home. He dresses up like a sailor with a sailor hat, a sailor bandana around his neck, red top, black underpants and blue gloves. He most likely Patrick's favourite superhero due to Patrick mainly dresses up like him. Unlike Mermaid Man, Barnacle Boy is smart and tries to the more sensible thing.Barnacle Boy's friendship with Mermaid Man can be a very stressed at times Barncle Boy walked over to the dark side just because Mermaid Man orded him a kiddy meal for him at the Krusty Krab. Barncle Boy states out that he dosen't like being called Barnacle Boy, but instead, would prefer to be called Barnacle Man and he sometimes calls Mermaid Man an "Old Coop".