On December 18, 2015, Vincent Waller, tweeted some early production work of the first Season 10 episode.
The old man cries because he doesn't get to have fun but Sandy and Sponge Bob hook Sponge Bob's propeller onto the old man so he can fly in the air too and he is having fun as the episode ends. According to Vincent Waller, the production of season 10 began on October 12, 2015.
The Curse of Bikini Bottom / Squidward in Clarinetland134. Back to the Past / The Bad Guy Club for Villains136.
The Monster Who Came to Bikini Bottom / Welcome to the Bikini Bottom Triangle141.
So when a show does achieve that milestone, they plan something big to not only draw ratings, but to break out into the three digit episodes.
Part of the celebration is that pure money is offered with syndication rights, which a general rule of thumb is to have 100 episodes to air in certain time slots like does.
They are made, and even if they get a chance on the air, the vast majority of them fail within a few weeks.
With other shows, they sometimes will build up a dedicated audience that will fail to keep the show alive long enough. Most full television seasons are between 20 and 26 episodes long.It may avoid all of that and the installment is just given an additional polishing to make it one of the best episodes of the series.But no matter what, remaining in the public view for years is an impressive event in any form of media. Sandy's detector leads to the same old man who found their brains. But Sandy just walks in, and they try to look for the brains. Sponge Bob calls Sandy on the phone and she uses a missing brain detector to find the brains. Sponge Bob accidentally trips onto the barrel, and all the brains fly free, and all go back to their original being.