Rock Buddy is a character that was briefly seen in the episode "Bubble Buddy."
Role in episode
SpongeBob is lonely because none of his friends are available to play with him. As a result, he resorts to befriending inanimate objects. He creates Stick Buddy to play with, but it falls over. He then finds a pile of rocks he thinks he can play with and calls them "Rock Buddy." After the rock pile doesn't do anything, he moves on to Sink Buddy, and finally succeeds with Bubble Buddy.