Muscel Man

Mitch Sorenstein "Muscle Man" is one of the Groundskeepers at the park

Personality and Traits
Muscle Man is a type of monster and/or disfigured human that works in the park along with Mordecai and Rigby. Although Benson considers him to be hard-working, Muscle Man is a slacker. He (along with High Five Ghost) has been revealed to do more work than Mordecai and Rigby in Muscle Woman, though they tend to slack off more than Mordecai and Rigby. In My Mom, it's shown that he has a lot of friends, most in which love his constant "My Mom!" jokes, which everyone else at the park gets annoyed with. He's best friends with High Five Ghost, who loves his jokes. Ignorant yet clever when it comes to pranks, he's always either insulting Mordecai or Rigby, or trying to prank them (ex. "My Mom", "See You There"). But he does care about his mom as shown in My Mom when he got very angry when Mordecai and Rigby made fun of his mom. In response, he brought his brother, John, to give Mordecai and Rigby a punishment for ridiculing their mother.

Despite being obese and lazy, there is a story behind Muscle Man's nickname (as revealed in Peeps ). In the episode, he said that he is losing muscle mass from the stress Peeps put on him, so he may have muscle mass.

Starla
Starla is Muscle Man's girlfriend that is seen in Muscle Woman. Muscle Man has been dumped by Starla 2 times, presumably for not willing to share his feelings.

High-Five Ghost
High-Five Ghost is to Muscle Man as Rigby is to Mordecai, because we don't see then together as much, we can't be sure. Mordecai shows affection for Rigby much more than Muscle Man does to HFG. They are usually seen together in the episodes. He usually gives a high five right after Muscle Man says a "My Mom" joke. In " My Mom! ," the two seem to slack-off as much as Mordecai and Rigby.

Mordecai
Out of the two protagonists, Mordecai seems to dislike Muscle Man more. He is annoyed by the constant "My Mom" jokes and even confronts Muscle Man about it in " My Mom! ". Besides that episode, there is not much interaction. Muscle Man does throw his shirt at Mordecai in " Caffeinated Concert Tickets ", but that may have been an accident rather than a direct confrontation. He may have been doing this just so that they would not have to do his work.

Rigby
Rigby seems to like Muscle Man slightly more than Mordecai. He likes to hang out with him in " My Mom! ", and seems to get along with him very well, yelling "Ohhhhhh!" along with him at the taco truck. They do have some confrontations though. In " Meat Your Maker ", he goes to say Muscle Man pushed him at a party (though Mordecai quickly says Muscle Man was not even there). Also by the end of " My Mom ", Rigby goes on to say how he hates Muscle Man. Also in " Death Punchies ", Muscle Man is forced to be look out, even though his eyes were punched out by Rigby. They also hang out in " The Night Owl ".

Benson
Benson trusts Muscle Man far more than Rigby and Mordecai, as established in " Appreciation Day " and " My Mom ". He does fire Muscle Man though in " Don ", but this may be due to the stressful situation that everyone was in. Benson also seems to understand Muscle Man and his antics, as demonstrated in " But I Have A Receipt " and " Free Cake ", not yelling at Muscle Man when he put "My Mom" on the list. He does not confront Muscle Man when he unzips his pants in " Free Cake ", saying, " It's not that kind of party, Muscle Man."

John
John is Muscle Man's little brother.

Scott D.
Scott D. is the person in charge of the getting people to the Crash Pit. When Muscle Man and High Five Ghost find a car to run into the Crash Pit he gets people to watch.

Skull Punch
Skull Punch are Muscle Man and High Five Ghost's enemies. When they get their RV to drive it into the crash pit. they fight them.

Low Five Ghost
Low Five Ghost is High Five Ghost's Brother. Muscle Man and High Five Ghost

Bobby
Bobby works at the nursery he helps people carry heavy plants. Him and Muscle Man are freinds. He thinks Muscle Man's "My Mom" jokes are hilarious.

Jimmy
Jimmy works at the TV Warehouse and owes Muscle Man something. He got fired for giving him a TV so that they can beat the hammer.

Trivia
keepers at the park .
 * High-Five In the episode Muscle Woman, his real name is revealed to be Mitch Sorenstein.
 * Muscle Man also appears to be drawn similarly to characters from "The Marvelous Misadventures of Flapjack", a Cartoon Network cartoon J.G. Quintel worked on before starting Regular Show.
 * More often than not, Muscle Man removes his shirt during the episode he appears in.
 * Muscle Man likes Fist Pump and drinks soda.
 * Muscle Man's "My Mom" jokes are similar to "Your Mom" jokes, but Muscle Man words the jokes so they insult himself rather than others, which is the intention of "Your Mom" jokes
 * Muscle Man's voice tone turned lower after Caffeinated Concert Tickets.
 * Muscles Man's catchphrase for getting hurt is "Oh no, bro.", which is seen in Death Punchies and Rage Against the TV.
 * He was seen checking out Margaret as shown in " First Day ", though they haven't interacted since.
 * In Over The Top Muscle Man lasted the longest in the arm wrestling match, which means he is very strong, and probably why he is called Muscle Man.
 * He thinks an internet sensation called Wedgie Ninja is funny.
 * In the episode "Karaoke Video", it is shown that he sometimes carries and emergency bag of gravy strapped to his chest.
 * Muscle Man flails around and shakes tables when in pain
 * Even though Muscle Man was fired in " Don " he still works at the park in the next episode.
 * Muscle Man resembles Yajrobe from Dragon Ball Z with his voice, body shape and attitude
 * Muscle Mans shown/known family is similar to Al Borlands family on Home Improvement, both have brothers that look similar to them, and both have unseen moms.
 * Throughout at least the second season, there is reference to Muscle Man having some sort of odor. In The Night Owl, Mordecai says that he smells like barf, but this is never again touched upon.