Squidward's Birthday: Squidward's birthday is coming up and
Spongebob tries to help him celebrate it.
Cousin Carl: Patrick's cousin, Carl is coming to visit the Bikini Bottom after being under some stress in the big city,Coral City.
Snail Sister: Spongebob finds a stray snail and takes it in, Gary recognizes it as his own sister.
Neighboring(SPECIAL(new character)):Spongebob gets a new neighbor that has a pet snail.
I'll post more soon, you should add ideas too!