Proving again why he’s one of Hollywood’s top-rated character actors, Oscar-nominated WILLIAM H. MACY – who stars as a scruffy, long-haired alcoholic creep on Showtime’s popular hit “Shameless” series – actually got busted as a “vagrant” by Chicago cops!

Revealed an on-set source: “During an outdoor location shoot downtown, Bill needed to take a quick potty break – but rather than walk way back to his dressing trailer, he ducked into a nearby restaurant. Making his way to the restroom area, he was stopped by two Chicago policemen who’d spotted his wild, dirty hair and ratty clothing, assumed he was a drunken vagrant – and were ready to escort him out the door!”

Amused at first, Macy joked: “Hey, I really look the part, right?” Then, realizing the cops were dead serious, he quickly explained who he was – and that he plays a drunk on a TV show. Luckily, an assistant director walked into the restaurant just then and confirmed Macy’s identity to the cops, who released their grip and apologized.

Said the source: “Bill just laughed and invited the cops to come watch them film when they were off duty – but they never showed up.”