Hi Five Ghost

High Five Ghost, also nicknamed High-Five or even just Fives (by Muscle Man) is a ghost who works alongside Mordecai and Rigby as a groundskeeper at the park.

Appearance
High-Five Ghost ( Or "Fives", as Muscle Man calls him) is a small, pale ghost. He is semi-transparent as you can see through him, but not completely through. He has basic features, eyes and a mouth, but also has one hand sticking out of his head. He has two other arms which are hidden.

Muscle Man
He and Muscle Man seem to be close friends, since they are always assigned jobs together. When Muscle Man is in a frame, it is to be assumed that "Fives" is along with him. The two are inseparable, just like Mordecai and Rigby.

Mordecai and Rigby
Though they have little interaction, in the episode, Muscle Woman, High-Five Ghost tells them that there is only one way to help Muscle Man. He is also smiling with Rigby when it is revealed that Starla likes Mordecai.

Other Employees
High-Five Ghost does not seem to communicate with the workers at all. He usually remains silent, but does obey orders.

Times High-Five Ghost Speaks
In Just Set Up The Chairs, Fives (along with Muscle Man) says "YES! Uh!" when they are chosen to pick up The Special Entertaiment.

In Rigby's Body, High-Fives asks Rigby "What are you!?" while working in The Snack Bar with Muscle Man.

In My Mom, Fives is shown saying "OHHH!" with Muscle Man and The Taco Worker, but he is barely heard, and some believe he isn't heard at all. He probably isn't heard because Muscle Man's voice is extremely loud when he shouts/yells also he hollered WHOO!!!

In Rage Against the TV, he says "Uh huh".

In Benson Be Gone,High-Five Ghost screams in pain as his hand grows back.

In Muscle Woman, he speaks twice and with full sentences. He sounds just like Mordecai only more "ghostly". The first time is to tell Mordecai and Rigby what is wrong with Muscle Man. The second time is to tell the duo where Starla works.

In Temp Check, he can be heard speaking while playing basketball saying "Cover him!"

In Jinx, he speaks four times. When Rigby asked High-Five Ghost why he won't say his name three times, Fives responds by saying "Because I'm jinxed, too." Fives gets ambushed by Muscle Man pleading to Rigby "Help me" and making MM punch him again. After Rigby said High-Five Ghost's name three times, Fives laughed and hollered "WHOO!" and flew away. He also yelled for Muscle Man in distress when the Jinx Monster attacked MM.

In See You There he has spoken by far the most times, being the main character in the episode.

Trivia

 * Despite his name, High-Five Ghost is shown to only have four fingers.
 * He and Muscle Man can be seen with the crowd of people in the Pilot episode watching Mordecai and Rigby playing Rock, Paper, Scissors.
 * When Muscle Man is fired in Don, High-Five Ghost goes with Muscle Man, even though High-Five is not fired.
 * It is unsure if he's as arrogant as Muscle Man, although he does seem to agree with the insults Muscle Man calls out to Mordecai and Rigby.
 * High-Five Ghost's nickname is Fives when Muscle Man and him flee after Muscle Man thinks that a "bucket with wheels" stole Rigby's voice in the episode Rigby's Body.
 * Despite being a ghost, he is touchable, proven by hi-fiving and getting punched by Rigby in Death Punchies and Muscle Man in Jinx.
 * High-Five Ghost wears spiked brass knuckles when Rigby's consciousness was emptied into the garbage truck.
 * In Rigby's Body, we finally hear him speak when he says to Rigby "What are you?" In the episode Just Set Up The Chairs he can be heard saying "Yes! Uh!" with Muscle Man, though this is barely heard.
 * High-Five Ghost is almost always smiling.
 * High-Five Ghost first frowns when he carries Rigby down from the roof in Death Punchies.
 * High-Five Ghost is a ghost, but it is not explained who he is the deceased form of.
 * In the episode, My Mom, High-Five Ghost actually has three arms instead of one located on top of his head. His other two arms are on the sides.
 * High-Five might be a parody of the ghosts on Pac-Man.
 * High-Five's hand on his hand looks like a fork, while his other two hands that come out of the side of him have 5 fingers and actually look like human-hands.
 * In Just Set Up The Chairs, it is the first and only time High-Five smiles without his mouth open.
 * Even though it is shown Fives has two other hands, he often does more stuff with his top hand on his head.
 * It is shown that Muscle Man's Uncle John taught High-Five how to fix the engine in the golf-cart to make it go speeding fast. Though, Muscle Man probably was lying, because Fives high-fived him afterwards. Though it's possible that he was saying it was cool that his Uncle John taught him.
 * It's possible that High-Five is also hurt when someone says that Muscle Man doesn't say his jokes right.
 * High-Five Ghost is a great bowler as proven in My Mom.
 * High-Five Ghost enjoys watching football with Muscle Man, as proven in Peeps.
 * High-Five Ghost holds up the rock sign many times in My Mom.
 * High-Five Ghost likes to annoy Benson, along with Muscle Man.
 * High-Five Ghost is a fan of Fist Pump.
 * In Death Punchies, it's unknown why Rigby punches him because he is not shown to have beaten Rigby at Punchies. Also, he is shown to be hit but he is not shown with Muscle Man smashed into the building.
 * When High-Five shouts "OOOOOHHHH!" with Muscle Man and the Taco Shop Worker, he is not heard.
 * High Five Ghost has many nicknames, including High-Five, High-Fives, Fives, HFG, and Five.
 * In the episode Benson Be Gone, High-Five turns to normal becuase he didn't do what Susan says and then drinks a whole can of soda.
 * It is possible that the way High-Five Ghost looks in Benson Be Gone is a reference to the killer in the horror movie, Scream.
 * This Is My Jam marks the biggest exspression on High-Five's face and also marks the only time he frowns with his mouth open.
 * High-Five Ghost is voiced by JG Quintel, but is voiced by Jeff Bennett in early episodes
 * High-Five Ghost's facial expressions resemble those of the faces of Comedy and Tragedy that are in plays and theaters.
 * In Jinx, he was unaffected by the Jinx monster's scratch probably due to intangibility, though he didn't use it when punched by Muscle Man.
 * In See You There, Low-Five, his brother says that ghosts can't be hurt but he is punched multiple times by MM in Jinx and hurt and pummeled by the Hammer in "Rage Against the TV".