He is a cave sponge from the cavemen years in B.C (Before Comedy/Before Common) and looks similar to SpongeBob, but with a messier smile and worn-out clothes and black shoes. He also has facial hair, wrinkles, and a lump on his head. He has buck teeth like SpongeBob, albeit more rounded. His shape and posture are slightly different from SpongeBob's.
Spongy Spongy is unfrozen from his cave after SpongeBob pours some hot chocolate onto Patrick's tongue which is stuck on the ice. Spongy Spongy follows SpongeBob around, aroused by his shoes. Due to him destroying everything in an attempt to mimic everything SpongeBob does, he gets his current generation offspring framed.
Meanwhile, Spongy is in the Krusty Krab kitchen, messing around when Squidward finds him. Squidward thinks he is actually SpongeBob and let out of prison early. Squidward tells him to get food ready, so Spongy Spongy goes to the back to hunt. Due to the modern Bikini Bottom being civilized, he can't hunt for animals, so he attacks a car and uses the parts as ingredients.
After the food is served, everybody complains, making Squidward think SpongeBob has gone crazy.
Spongy then runs all the way to the Bikini Bottom Town Hall and finds SpongeBob there. The two of them then talk and compare how similar they are. Afterwards, Spongy Spongy stomps so hard that he destroys the town hall, but is instead set free because they wanted it to come down in a week.