Frank Medrano is best known for playing a guy named Fat Ass in "Shawshank Redemption" -- and one named Fat Mancho in "Sleepers" -- so maybe it's a good thing the cops impounded his car Saturday night ... walking is good for you.
Law enforcement sources tell TMZ Medrano was pulled over for making an unsafe lane change. We're told when cops ran his license, they discovered it was suspended ... so they impounded his 2007 Cadillac for 30 days.
It's a good thing cops didn't lock him up, otherwise he'd have been yelling "I don't belong here! I want to go home!" ("Shawshank" joke. Great movie.)