Rock Buddy is a pile of rocks that only appears briefly in the episode "Bubble Buddy."
Rock Buddy is simply a small pile of dark gray rocks.
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 first creates Stick Buddy, 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 does not do anything, he moves on to Sink Buddy, and finally succeeds with Bubble Buddy.