|Relatives:|| Muscle Man's Mom (wife)|
Muscle Man (son)
|Voiced by:||Fred Tatasciore|
|Appears in:||"Trucker Hall of Fame"|
Muscle Dad Sorrenstein is Muscle Man's deceased father. He appeared in "Trucker Hall of Fame". He was known as a trucker, but was actually a forklift operator. He loved to prank truckers, people, and even Muscle Man himself. Mordecai, Rigby and Muscle Man call him "Muscle Dad."
He appears to be overweight like Muscle Man, had a white undershirt, and blue jeans. He also has a brown belt with a gold buckle, black overalls with silver connecters, brown cowboy-like boots, and a trucker net-hat that is red and has "World's Greatest Trucker" on it. He has a brown connecting mustache, bushy brown eye-brows, and black shoulder hair.
- He is the sixth family member of a park worker to appear on Regular Show.
- Similar to Muscle Man's "my mom" jokes, Muscle Man's dad says "my wife".
- His hat looks similar to the "I'm Eggscellent" Net Hat. Except his hat is red, while the Eggscellent Net Hat is blue.
- According to the synoposis for "Trucker Hall of Fame," he recently died after he got mauled from putting a cactus under a cop in a bear costume who was actually a real bear.
- Like Muscle Man, he loves pulling pranks, like the one he did with the air horn.
- He always wanted Muscle Man to be proud of him.
- Since he was called Muscle Dad, it is possible that Muscle Man's mom is called Muscle Mom.
- None of the people he worked with liked him.
- Since Muscle Man isn't Muscle Man's real name, it can be assumed Muscle Dad isn't his real name.