Spongebob worked so well because it was very much a gag-driven show. All of the best episodes had a very simple plot line that could be described in one sentence, and the writers just filled the 11 minutes with the best jokes they could come up with on the subject.>Bubblestand
SpongeBob gives lessons on how to blow bubbles.>Pizza Delivery
SpongeBob and Squidward deliver a pizza.>The Secret Box
SpongeBob tries to find out what's in Patrick's secret box.>Procrastination
SpongeBob procrastinates writing an essay.>Squid on Strike
SpongeBob and Squidward go on strike.>No Weenies Allowed
SpongeBob tries to get into a tough-guy club.>Krusty Krab Training Video
The description is literally the title.>Chocolate with Nuts
SpongeBob and Patrick sell chocolate bars.
With these episodes, while most of them had a clear beginning and end, you probably couldn't remember exactly what order the stuff in the middle happened in. After season 3, they started to run out of ideas that fit this simple structure and the episodes became more story-driven. It was like the jokes were more of an afterthought instead of what the entire episode was based around.