How old is muscle man in regular show?

Muscle Man's age is never explicitly stated in Regular Show, and it's often played for laughs as being a mystery even within the show itself. He's shown to be very immature and childlike, but also seems to have some very old-fashioned ideas.

There are some hints that might suggest his age:

* He mentions having a "grandfather" who is a pirate in "The Power." This could suggest that Muscle Man is at least a few generations removed from a pirate, potentially placing him in his 50s or older.

* He claims to be "older than the internet" in "The Power." This, however, is likely a hyperbole, as the internet has only been around for a relatively short time.

* He doesn't seem to age much in the series, despite having a long history with Mordecai and Rigby. This further supports the idea that he might be significantly older than them, but possibly immortal or simply aging at a much slower rate.

Overall, it's safe to assume Muscle Man is at least in his 40s, but possibly much older. His age is a running joke, and it's best to consider it an unknown factor in his personality and comedic appeal.