Stephen Hillenburg thought of the characters for SpongeBob SquarePants in 1984, while teaching and studying marine biology. During this time, Hillenburg began working on animation and began writing a comic book called “The Intertidal Zone” which featured a number of sea creatures as the main characters. Many of them would eventually become SpongeBob SquarePants characters, including "Bob the Sponge".
There are seven main character to the famous TV series SpongeBob SquarePants - SpongeBob SquarePants, Patrick Star, Squidward Tentacles, Eugene H. Krabs, Sandy Cheeks, Sheldon J. Plankton and Gary the Snail. These seven characters are seen in a majority of the series episodes. Other than the main seven, there are more than twenty reoccurring characters throughout the nine seasons.
While most of the characters gained a lot of popularity, none did so more than the main character, SpongeBob. In 2002, SpongeBob SquarePants dolls sold at an astounding rate of 75,000 per week, which was faster than Tickle Me Elmo dolls were selling at the time. After gaining much notoriety, SpongeBob made appearances in several other animated shows such as South Park, Family Guy, The Simpsons and others.

[new page = 10. Squilliam Fancyson]
Squilliam Fancyson

Squilliam is Squidward archenemy. He has everything Squidward wants. He is also the only character on the show that can make Squidward blush.

[new page = 9. Patchy the Pirate]
Patchy the Pirate

Patchy the Pirate is the narrator and creator of the Spongebob fan club. He also sings the show’s theme song. He is one of the only human characters throughout the show and quite often shares his opinion on various episodes.

[new page = 8. King Neptune]
King Neptune

Neptune in the king of the sea and makes an appearance every so often throughout the show. His most famous episode involves SpongeBob facing him in a krabby patty making contest. He is very funny and quite often ends up eating his words. He isn’t the smartest king.

[new page = 7. Man Ray]
Man Ray

Man Ray is one of Mermaid Man and Barnacle Boy’s enemies. Man Ray has a man's body with a stingray's head. He is not a very good villain but is good for laugh. The clip above is from his best episode.

[new page = 6. Pearl Krabs]
Pearl Krabs

Pearl Krabs is Mr. Krabs’ daughter. For some reason she is a whale. She is very funny in most cases when she wants to use her father’s money. Needless to say, her father, Mr. Krabs, loves money and hates spending it. The only downside to her character is her voice. She is often loud and obnoxious.

[new page = 5. The Flying Dutchman]
The Flying Dutchman

This show wouldn’t have been complete without a ghost pirate. The Flying Dutchman shows up now and then on a number of SpongeBob’s adventures. Quite often he is terrorizing the citizens of Bikini Bottom in very funny ways.

[new page = 4. Mrs. Puff]
Mrs. Puff

Mrs. Puff is the driving instructor for Bikini Bottom. She hates SpongeBob because he is the most incompetent driving student she has ever had. Most of her comedy comes through SpongeBob making her life miserable.

[new page = 3. Larry the Lobster]
Larry the Lobster

Larry is a body building lobster that lives in Bikini Bottom. He is often showing off his muscles and lifting weights on the show. He is also the local lifeguard as seen in the above video with the little bit of sunscreen on his nose.

[new page = 2. Karen]
Karen

Karen is Plankton’s computer wife. However, ‘WIFE’ is an acronym for Wired Integrated Female Electroencephalograph. She is often helping Plankton scheme towards stealing the krabby patty formula. The humor with her comes through Plankton rejecting her ideas but actually taking them as his own ideas.

[new page = 1. Mermaid Man and Barnacle Boy]
Mermaid Man and Barnacle Boy

These two are elderly superheroes of the sea. While Mermaid Man is the leader, he doesn’t appear to be as Barnacle Boy is much smarter. Mermaid Man is famous for randomly yelling ‘EVIL!’ The two have good chemistry and are very funny in their quests to stop and destroy evil. SpongeBob is their biggest fan.