Well this was fun! I was bored and decided to take all of the information from the show that I remembered and made a history of the ocean world! Of course, it can't be taken too seriously; I made it because I had fun with it! 
But still, if anyone remembers any event that I'm missing, let me know. Also let me know if I misstated anything. This should be as perfect as possible!
The History of Bikini Bottom
In prehistoric times, Bikini Bottom has not formed yet, and there is no civilization. Creatures wander freely. Squidward arrives from the future and discovers "Jellyfishing".
Decades later...
100,000,000 years before the present, life has evolved, a language is formed, but is still in prehistoric times. SpongeGar, Patar, and Squog discover fire.
Millions of years pass.
Roughly 400 years before the present is the Medieval Era, the age of the Bikini Bottomshire, ruled by King Krabs, who is in war with the Lord Planktonimore. There is a prophecy that two knights will fall from the sky and defeat Lord Planktonimore and his Dragon/jellyfish. This turns out to be SpongeBob and Patrick, who fall from the sky. With the help of the Dark Knight, ancestor of Sandy, they save Bikini Bottomshire.
A few centuries later.
About 100 years before the present is the Wild West era. In the place of Bikini Bottom Shire is Dead Eye Gulch, which is run by Dead Eye Plankton. SpongeBuck SquarePants comes to Dead Eye Gulch and must face him at high noon. In the process he meets his new "Idiot Friend", Patrick Star. At high noon, SpongeBuck beats Dead Eye Plankton by stepping on him. Dead Eye Gulch is renamed Bikini Gulch, and a statue of SpongeBuck is built. Finally, SpongeBuck and Patrick finish off by singing about their new friendship, with a song called "Idiot Friends".
Within a few decades, Bikini Bottom is formed from Bikini Gulch, in a time when the ocean is protected by Mermaid Man and Barnacle Boy. During a battle against Manray, from time machines, many SpongeBobs, Patricks, old Mermaid Mans, Barnacle Boys, and two Manrays appear.
The present era.
Over thirty years after SpongeBob becomes a fry cook, King Neptune's crown is stolen, and SpongeBob and Patrick rescue it. SpongeBob is named the manager of the Krusty Krab 2.
2000 years pass.
The world is covered in chrome, and there are aliens, clones, and robots. Through a time machine, Squidward arrives in this era and is greeted by SpongeTron. Also, somewhere in a part of Bikini Bottom not covered in chrome, aliens discover strange giant statues that carry music with the wind. Jellyfish are attracted to this.
One eternity into the future.
In the remains of the Krusty Krab, long after the chrome era ends, the skeletons of SpongeBob and Squidward are still working in the Krusty Krab. It is unknown whether or not the Krusty Krab 2 still exists in any form.
