Well i would call it Spongebob 2: The Grand Finale. And what would happen would be that Spongebob has a baby bye a woman called Spongesam whom he met with in Season 8 and that baby would be named Baby Reef. And the Squarepants' would become so caught up with the baby that he didn't have time to play with his friends. Later, Spongebob feels sorry and gives them all gifts. He gives Squidward a recording contract, he gives Sandy a scientist contract, he gives Mr. Krabs a million dollars, collected by donation, he gives Patrick a brain, and he gives Marty, introduced in Season 8, a sofa. At the end of the episode, they have a party in the Krusty Krab and Spongebob reveals what the secret formula is.

WHatever the ending is, it has to involve a conclusion for spongebob, patrick, squidward, gary, krabs, pearl, puff, plankton, sandy.

I would have it thatplankton and krabs unite to face a force who is has been secretly trying to get the formula as well besides plankton. Someone has kidnapped squidward and the rest, and spongebob must find them.

Towards the end, it turns out Patrick has been actin dumb the entire series in order to get close to the formula, which is the best to ever be created, and insures its owner vast wealth. Spongebob and patrick fight in front of the rest of the gang to decide the fate of seas. In the end, when patrick has spongebob pinned and about to finish him, he gets a good dose of talking too by the gang and spongebob, and eventually decides himself to stop. He realizes he loves spongebob as a freind and truly doesnt want to hurt him. He gives up and releases everyone.

He is forgivven and everyone apologizes for making fun of him, and turning him evil. He accepts, and apologizes, then they all get their own little conclusion.

The past 10 minutes or so we fast foraward, and everyone is dead, and it shows kids playing, people working, then a new gang of people are shown, and the narrator hints at a spinoff.

Spongebob and patrick and the rest are gone. But the show goes on with a new cast.