Pete is a bluish black rock with white googly eyes and a drawn-on mouth.
He is given to SpongeBob by Patrick. SpongeBob plans on throwing it away until Patrick teaches him about the sentimental value of it, then SpongeBob decides to keep it along with most other stuff he was going to throw away.
At some point, SpongeBob lost Pete and it ended up in the Krusty Krab lost and found.
Pete the Rock is similar to one of Patrick's masterpieces in the episode "The Googly Artiste."