It's the first episode of the Spongesons.
Spongebob and Patrick are jellyfishing. Sandy is working on a jellyfish sonar. Mr. Krabs is looking for hidden money, and Squidward is running from the jellyfish Spongebob and Patrick are trying to catch. Suddenly, a whirlpool throws them into a portal.
They fall into Springfield and crah into the Simpson home. Bart pranks them by doing the pants wet via bucket trick, but it instead brings them back to life. They are soon questioned. After explaining how they got there, Homer decides to throw them out onto the street.
Marge scolds Homer, telling him to let them stay. Homer then invites them in, against his will. Lisa then performs an elaborate jazz song to welcome Spongebob and his friends. A mix of the Simpsons theme song and the Spongebob theme is used over the credits
Originally, the Simpsons would throw them into a trash can in downtown, but it was made the area in fornt of their house for some reason.