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This article is about Muscle Man's older brother. For Margaret's cousin, see here.

John "Muscle Bro" Sorrenstein
John Sorrenstein 1
Biographical Information
Occupation: Unknown
Species: Human
Gender: Male
Hair color: Brown
Relatives: Muscle Dad (father)
Muscle Man's Mom (mother)
Muscle Man (younger brother)
Starla (sister-in-law)
Unnamed nephews
Unnamed nieces
Show Information
Voiced by: Steve Blum
First appearance: "My Mom"
Latest appearance: "Dumped at the Altar"

John Sorrenstein, a.k.a. "Muscle Bro", is a character who first appeared in the episode "My Mom".


Even though Muscle Man resembles a zombie, monster, or a disfigured humanoid with green skin, his brother has pale red skin and resembles a tall, plump, grown man. It is revealed that he's older than Muscle Man because he calls him 'little brother' on the radio. He arrives to teach Mordecai and Rigby a lesson on making fun of their mom, though this was simply a prank they had planned. He also appears in "Trucker Hall of Fame", where he delivers the grim news of Muscle Dad's death to Muscle Man, and then he's seen in a flashback where he strikes a piñata and scorpions fall on him. He also makes a cameo appearance in "Pie Contest". He reappears in "Trailer Trashed" where he helps Muscle Man save his trailer with his truck.


Season Two

Season Three

Season Four

Season Five

Season Six


  • Unlike Muscle Man and their father, he looks more like a human being.
  • His hair looks like the hair on the picture of Muscle Man's mom, which was shown to Mordecai and Rigby.
  • He bears a resemblance to Lolly Poopdeck from The Marvelous Misadventures of Flapjack, which JG Quintel also worked on, as well as Carl Brutananadilewski from Aqua Teen Hunger Force.
  • His legs are oddly long for his body.
  • In "Trucker Hall of Fame" and "Trailer Trashed", Muscle Man calls him Muscle Bro.
  • It is revealed in "Trucker Hall of Fame" that he was pranked on his birthday when Muscle Dad and Muscle Man put scorpions in his piñata instead of candy.


Season Two

"My Mom"

Season Three

"Trucker Hall of Fame"

Season Four

"Pie Contest"

"Trailer Trashed"

Season Five

"Every Meat Burritos"

"The Thanksgiving Special"

Season Six

"Terror Tales of the Park IV"

"The End of Muscle Man"

"Dumped at the Altar"

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