High Five Ghost is a ghost who works alongside Mordecai and Rigby as a groundskeeper at the park. He and Muscle Man seem to be close friends, since they are always assigned jobs together. Strangely, High-Five Ghost does not speak as much as the other characters, although when he does, he has a rather high-pitched, echoing, wavering voice. His name is evident because he has what looks like a hand on his head and often high-fives Muscle Man with it.
He, along with Muscle Man, appeared in numerous episodes and they both got a Grammy and a Lobscar Award along with other different characters.